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Product listing: Anti-Blue (2D2F11) Mouse mAb (HRP Conjugate) #46387 to p44/42 MAPK (Erk1/2) Blocking Peptide (#4695 Specific), UniProt ID P27361 #1240

$224
10 western blots
100 µl
Anti-Blue (2D2F11) Mouse mAb is conjugated to the carbohydrate groups of horseradish peroxidase (HRP) via its amine groups. This product has been optimized to detect proteins labeled with remazol blue.
APPLICATIONS

Application Methods: Western Blotting

Background: Chemiluminescence systems have emerged as the best all-around method for western blot detection. They eliminate the hazards associated with radioactive materials and toxic chromogenic substrates. The speed and sensitivity of these methods are unequalled by traditional alternatives, and because results are generated on film, it is possible to record and store data permanently. Blots detected with chemiluminescent methods are easily stripped for subsequent reprobing with additional antibodies. HRP-conjugated secondary antibodies are utilized in conjunction with specific chemiluminescent substrates to generate the light signal. HRP conjugates have a very high turnover rate, yielding good sensitivity with short reaction times.

$107
350 µl
Color-coded Prestained Protein Marker, Broad Range (11-250 kDa) is a mixture of purified proteins, covalently coupled to blue, green or orange dyes, that resolves to 12 bands between 11 and 250 kDa when subjected to electrophoresis. The protein concentrations are carefully balanced for even intensity. The covalent coupling of dye to protein affects the electrophoretic mobility in SDS-PAGE gels relative to uncoupled proteins. The apparent molecular weights of the prestained proteins are shown in the gel image.
APPLICATIONS
REACTIVITY
All Species Expected

Application Methods: Western Blotting

$30
25 µl
$107
250 µl
Color-coded Prestained Protein Marker, High Range (43-315 kDa) is a mixture of purified proteins, covalently coupled to blue, green, orange, or pink dyes, that resolves to 8 bands between 43 and 315 kDa when electrophoresed. The protein concentrations are carefully balanced for even intensity. The covalent coupling of dye to protein affects the electrophoretic mobility in SDS-PAGE gels relative to uncoupled proteins. The apparent molecular weights of the prestained proteins are shown in the gel image.
APPLICATIONS
REACTIVITY
All Species Expected

Application Methods: Western Blotting

$30
25 µl
$107
250 µl
Color-coded Prestained Protein Marker, Low Range (1.7-42 kDa) is a mixture of purified proteins, covalently coupled to blue, green or orange dyes, that resolves to 6 bands between 1.7 and 42 kDa when electrophoresed. The protein concentrations are carefully balanced for even intensity. The covalent coupling of dye to protein affects the electrophoretic mobility in SDS-PAGE gels relative to uncoupled proteins. The apparent molecular weights of the prestained proteins are shown in the gel image.
APPLICATIONS
REACTIVITY
All Species Expected

Application Methods: Western Blotting

$42
50 µl
$85
350 µl
$347
1750 µl
Prestained Protein Marker, Broad Range (11-190 kDa) is a mixture of purified proteins covalently coupled to a blue dye that resolve to a series of 11 bands between 11 and 190 kDa following electrophoresis. The protein concentrations are carefully balanced for even intensity. The covalent coupling of the dye to the proteins affects their electrophoretic behavior in SDS-PAGE gels relative to unstained proteins.
APPLICATIONS
REACTIVITY
All Species Expected

Application Methods: Western Blotting

$64
650 µl
$228
3250 µl
Biotinylated protein ladder detection pack is designed to detect the molecular weight ladders on Western blots when using the horseradish peroxidase (HRP) based Western detection system. The pack contains Biotinylated Protein Ladder and Anti-biotin, HRP-linked Antibody. The molecular weight ladder is a mixture of purified proteins covalently coupled to biotin that resolve to 10 bands that have a size range of 9-200 kDa. The anti-biotin antibody is used to detect biotinylated protein ladders on Western blots. The pack is optimized for chemiluminescent Western detection procedures.
APPLICATIONS

Application Methods: Western Blotting

The Myosin Light Chain 2 Antibody Sampler Kit provides an economical means to detect total, phosphorylated, and dual-phosphorylated myosin light chain 2. The kit contains enough primary and secondary antibody to perform two western blot experiments.

Background: Myosin is composed of six polypeptide chains: two identical heavy chains and two pairs of light chains. Myosin light chain 2 (MLC2), also known as myosin regulatory light chain (MRLC), RLC, or LC20, has many isoforms depending on its distribution. In smooth muscle, MLC2 is phosphorylated at Thr18 and Ser19 by myosin light chain kinase (MLCK) in a Ca2+/calmodulin-dependent manner (1). This phosphorylation is correlated with myosin ATPase activity and smooth muscle contraction (2). ROCK also phosphorylates Ser19 of smooth muscle MLC2, which regulates the assembly of stress fibers (3). Phosphorylation of smooth muscle MLC2 at Ser1/Ser2 and Ser9 by PKC and cdc2 has been reported to inhibit myosin ATPase activity (4,5). Phosphorylation by cdc2 controls the timing of cytokinesis (5). Transgenic mice lacking phosphorylation sites on the cardiac muscle isoform show morphological and functional abnormalities (6).

The MYPT1 Antibody Sampler Kit is an economical way to examine the total protein levels of MYPT1 as well as MYPT1 phosphorylated at Ser507, Ser668, Thr853, and Thr696. The kit includes enough primary and secondary antibodies to perform two Western blot experiments.

Background: Protein phosphatase 1 (PP1) is a ubiquitous eukaryotic protein serine/threonine phosphatase involved in the regulation of various cell functions. Substrate specificity is determined by the binding of a regulatory subunit to the PP1 catalytic subunit (PP1c). It is estimated that over fifty different regulatory subunits exist (1).The myosin phosphatase holoenzyme is composed of three subunits: PP1c, a targeting/regulatory subunit (MYPT/myosin-binding subunit of myosin phosphatase), and a 20 kDa subunit of unknown function (M20). MYPT binding to PP1cδ alters the conformation of the catalytic cleft and increases enzyme activity and specificity (2). Two MYPT isoforms that are 61% identical have been described. MYPT1 is widely expressed, while MYPT2 expression appears to be exclusive to heart and brain (3). Related family members include MBS85, MYPT3, and TIMAP (4).Myosin phosphatase regulates the interaction of actin and myosin in response to signaling through the small GTPase Rho. Rho activity inhibits myosin phosphatase via Rho-associated kinase (ROCK). Phosphorylation of MYPT1 at Thr696 and Thr853 results in phosphatase inhibition and cytoskeletal reorganization (5,6).

The N6-mA Methyltransferase Antibody Sampler Kit provides an economical means of detecting N6-mA methyltransfearse proteins using control antibodies against METTL3, METTL14, WTAP, and Virilizer. The kit contains enough primary antibodies to perform at least two western blot experiments.

Background: Methyltransferase-like protein 3 (METTL3) and methytransferase-like protein 14 (METTL14) are the two catalytic subunits of an N6-methyltransferase complex that methylates adenosine residues in RNA (1). Methylation of adenosine residues regulates mRNA splicing, processing, translation efficiency, editing and stability, in addition to regulating primary miRNA processing, and is critical for proper regulation of the circadian clock, embryonic stem cell self-renewal, immune tolerance, response to various stimuli, meiosis and mouse fertility (2,3). In this complex, METTL3 functions as the catalytic methyltransferase subunit and METTL14 functions as the target recognition subunit by binding to RNA (4). In addition, the Wilms tumor 1-associated protein (WTAP) functions as a regulatory subunit and is required for accumulation of the complex to nuclear speckles, which are sites of RNA processing (5). Several studies suggest a role for this complex in cancer. METTL3 expression is elevated in lung adenocarcinoma where it promotes growth, survival and invasion of human lung cancer cells (6). In addition, WTAP is over-expressed in a number of different cancers and positively regulates cell migration and invasion in glioblastoma and cholangiocarcinoma (7,8).

The Necroptosis Antibody Sampler Kit provides an economical means of detecting total and phosphorylated proteins associated with necroptosis. The kit includes enough antibody to perform two western blots with each primary antibody.

Background: Necroptosis, a regulated pathway for necrotic cell death, is triggered by a number of inflammatory signals, including cytokines in the tumor necrosis factor (TNF) family, pathogen sensors such as toll-like receptors (TLRs), ischemic injury, and neurodegenerative diseases (1-3). The process is negatively regulated by caspases and is initiated through a complex containing the RIP and RIP3 kinases, typically referred to as the necrosome. Necroptosis is inhibited by a small molecule inhibitor of RIP, necrostatin-1 (Nec-1) (4). RIP is phosphorylated at several sites within the kinase domain that are sensitive to Nec-1, including Ser14, Ser15, Ser161, and Ser166 (5). During necroptosis, RIP3 is phosphorylated at Ser227, leading to recruitment and phosphorylation of MLKL at Thr357 and Ser358 (6). Phosphorylation of MLKL results in its oligomerization and translocation to the plasma membrane, where it effects membrane integrity (7-10).

This peptide is used to block NEDD8 (19E3) Rabbit mAb #2754 reactivity.

Background: Neural precursor cell-expressed developmentally downregulated protein 8 (NEDD8), also known as Rub1 (related to ubiquitin 1) in plants and yeast, is a member of the ubiquitin-like protein family (1,2). The covalent attachment of NEDD8 to target proteins, termed neddylation, is a reversible, multi-step process analogous to ubiquitination. NEDD8 is first synthesized in a precursor form with a carboxy-terminal extension peptide that is removed by either the UCH-L3 or NEDP1/DEN1 hydrolase protein to yield a mature NEDD8 protein (3,4). Mature NEDD8 is then covalently linked to target proteins via the carboxy-terminal glycine residue in a reaction catalyzed by the APP-BP1/Uba3 heterodimer complex and Ubc12 as the E1- and E2-like enzymes, respectively (5). An E3 ligase protein, Roc1/Rbx1, is also required for neddylation of the cullin proteins (6). Protein de-neddylation is catalyzed by a number of enzymes in the cell, including a "ubiquitin-specific" protease USP21, the NEDP1/DEN1 hydrolase and the COP9/signalosome (CSN) (7,8,9). In contrast to the ubiquitin pathway, the NEDD8 modification system acts on only a few substrates and does not appear to target proteins for degradation. Neddylation of cullin proteins activates the SCF (Skp1-Cullin-F-box) E3 ubiquitin ligase complex by promoting complex formation and enhancing the recruitment of the E2-ubiquitin intermediate (10). While NEDD8 modification of VHL is not required for ubiquitination of HIF1-α, it is required for fibronectin matrix assembly (11). Mdm2-dependent neddylation of p53 inhibits its transcriptional activity (12).

The Neurofilament Antibody Sampler Kit provides an economical means of evaluating neurofilaments. The kit contains enough primary and secondary antibodies to perform two western blot experiments per primary antibody.

Background: The cytoskeleton consists of three types of cytosolic fibers: actin microfilaments, intermediate filaments, and microtubules. Neurofilaments are the major intermediate filaments found in neurons and consist of light (NFL), medium (NFM), and heavy (NFH) subunits (1). Similar in structure to other intermediate filament proteins, neurofilaments have a globular amino-terminal head, a central α-helical rod domain, and a carboxy-terminal tail. A heterotetrameric unit (NFL-NFM and NFL-NFH) forms a protofilament, with eight protofilaments comprising the typical 10 nm intermediate filament (2). While neurofilaments are critical for radial axon growth and determine axon caliber, microtubules are involved in axon elongation. PKA phosphorylates the head domain of NFL and NFM to inhibit neurofilament assembly (3,4). Research studies have shown neurofilament accumulations in many human neurological disorders including Parkinson's disease (in Lewy bodies along with α-synuclein), Alzheimer's disease, Charcot-Marie-Tooth disease, and Amyotrophic Lateral Sclerosis (ALS) (1).

This peptide is used to block Neurofilament-L (C28E10) Rabbit mAb #2837 reactivity in dot blot protocols.

Background: The cytoskeleton consists of three types of cytosolic fibers: actin microfilaments, intermediate filaments, and microtubules. Neurofilaments are the major intermediate filaments found in neurons and consist of light (NFL), medium (NFM), and heavy (NFH) subunits (1). Similar in structure to other intermediate filament proteins, neurofilaments have a globular amino-terminal head, a central α-helical rod domain, and a carboxy-terminal tail. A heterotetrameric unit (NFL-NFM and NFL-NFH) forms a protofilament, with eight protofilaments comprising the typical 10 nm intermediate filament (2). While neurofilaments are critical for radial axon growth and determine axon caliber, microtubules are involved in axon elongation. PKA phosphorylates the head domain of NFL and NFM to inhibit neurofilament assembly (3,4). Research studies have shown neurofilament accumulations in many human neurological disorders including Parkinson's disease (in Lewy bodies along with α-synuclein), Alzheimer's disease, Charcot-Marie-Tooth disease, and Amyotrophic Lateral Sclerosis (ALS) (1).

The Neuronal Marker IF Antibody Sampler Kit II provides an economical means for labeling cell types and cell structures by immunofluorescence (IF-F).
The Neuronal Marker IF Antibody Sampler Kit provides an economical means for labeling neuronal structures by immunofluorescence (IF-F). This kit includes enough primary antibody to perform at least forty IF-F tests or two western blot experiments per primary antibody.
The NF-κB Family Antibody Sampler Kit II provides an economical means of detecting members of the NF-κB family. The kit includes enough antibody to perform two western blots with each primary antibody.

Background: Transcription factors of the nuclear factor κB (NF-κB)/Rel family play a pivotal role in inflammatory and immune responses (1,2). There are five family members in mammals: RelA, c-Rel, RelB, NF-κB1 (p105/p50), and NF-κB2 (p100/p52). Both p105 and p100 are proteolytically processed by the proteasome to produce p50 and p52, respectively. Rel proteins bind p50 and p52 to form dimeric complexes that bind DNA and regulate transcription. In unstimulated cells, NF-κB is sequestered in the cytoplasm by IκB inhibitory proteins (3-5). NF-κB-activating agents can induce the phosphorylation of IκB proteins, targeting them for rapid degradation through the ubiquitin-proteasome pathway and releasing NF-κB to enter the nucleus where it regulates gene expression (6-8). NIK and IKKα (IKK1) regulate the phosphorylation and processing of NF-κB2 (p100) to produce p52, which translocates to the nucleus (9-11).

This kit contains reagents to examine total protein levels of the five NF-κB/Rel family members: p65/RelA, RelB, c-Rel, NF-κB1 (p105/p50) and NF-κB2 (p100/p52).

Background: Transcription factors of the nuclear factor κB (NF-κB)/Rel family play a pivotal role in inflammatory and immune responses (1,2). There are five family members in mammals: RelA, c-Rel, RelB, NF-κB1 (p105/p50), and NF-κB2 (p100/p52). Both p105 and p100 are proteolytically processed by the proteasome to produce p50 and p52, respectively. Rel proteins bind p50 and p52 to form dimeric complexes that bind DNA and regulate transcription. In unstimulated cells, NF-κB is sequestered in the cytoplasm by IκB inhibitory proteins (3-5). NF-κB-activating agents can induce the phosphorylation of IκB proteins, targeting them for rapid degradation through the ubiquitin-proteasome pathway and releasing NF-κB to enter the nucleus where it regulates gene expression (6-8). NIK and IKKα (IKK1) regulate the phosphorylation and processing of NF-κB2 (p100) to produce p52, which translocates to the nucleus (9-11).

This kit contains reagents to examine the activation state and total protein levels of key components in the noncanonical NF-κB pathway: TRAF2, TRAF3, NIK, IKKα, p100, and RelB.
The NF-κB p65 Antibody Sampler Kit contains reagents to examine NF-κB p65/RelA phosphorylation at Ser468 and Ser536; acetylation at Lys310; and total p65 levels.

Background: Transcription factors of the nuclear factor κB (NF-κB)/Rel family play a pivotal role in inflammatory and immune responses (1,2). There are five family members in mammals: RelA, c-Rel, RelB, NF-κB1 (p105/p50), and NF-κB2 (p100/p52). Both p105 and p100 are proteolytically processed by the proteasome to produce p50 and p52, respectively. Rel proteins bind p50 and p52 to form dimeric complexes that bind DNA and regulate transcription. In unstimulated cells, NF-κB is sequestered in the cytoplasm by IκB inhibitory proteins (3-5). NF-κB-activating agents can induce the phosphorylation of IκB proteins, targeting them for rapid degradation through the ubiquitin-proteasome pathway and releasing NF-κB to enter the nucleus where it regulates gene expression (6-8). NIK and IKKα (IKK1) regulate the phosphorylation and processing of NF-κB2 (p100) to produce p52, which translocates to the nucleus (9-11).

This peptide is used to block NF-κB p65 (C22B4) Rabbit mAb #4764 reactivity in dot blot protocols.

Background: Transcription factors of the nuclear factor κB (NF-κB)/Rel family play a pivotal role in inflammatory and immune responses (1,2). There are five family members in mammals: RelA, c-Rel, RelB, NF-κB1 (p105/p50), and NF-κB2 (p100/p52). Both p105 and p100 are proteolytically processed by the proteasome to produce p50 and p52, respectively. Rel proteins bind p50 and p52 to form dimeric complexes that bind DNA and regulate transcription. In unstimulated cells, NF-κB is sequestered in the cytoplasm by IκB inhibitory proteins (3-5). NF-κB-activating agents can induce the phosphorylation of IκB proteins, targeting them for rapid degradation through the ubiquitin-proteasome pathway and releasing NF-κB to enter the nucleus where it regulates gene expression (6-8). NIK and IKKα (IKK1) regulate the phosphorylation and processing of NF-κB2 (p100) to produce p52, which translocates to the nucleus (9-11).

The Notch Activated Targets Antibody Sampler Kit provides an economical means of detecting target proteins of activated Notch. The kit contains enough primary antibody to perform four western blot experiments per primary antibody.
The Notch Isoform Antibody Sampler Kit provides an economical means to investigate Notch Signaling. The kit contains primary and secondary antibodies to perform two western mini-blots with each antibody.

Background: Notch proteins (Notch1-4) are a family of transmembrane receptors that play important roles in development and the determination of cell fate (1). Mature Notch receptors are processed and assembled as heterodimeric proteins, with each dimer comprised of a large extracellular ligand-binding domain, a single-pass transmembrane domain, and a smaller cytoplasmic subunit (Notch intracellular domain, NICD) (2). Binding of Notch receptors to ligands of the Delta-Serrate-Lag2 (DSL) family triggers heterodimer dissociation, exposing the receptors to proteolytic cleavages; these result in release of the NICD, which translocates to the nucleus and activates transcription of downstream target genes (3,4).

The Notch Receptor Interaction Antibody Sampler Kit provides an economical means to evaluate Notch signaling. The kit contains enough primary antibody to perform two western blots per primary.
The Nuclear Receptor Antibody Sampler Kit provides an economical means to evaluate the presence and status of nuclear receptors. This kit contains enough primary antibody to perform two western blots per primary.
NuRD Complex Antibody Sampler Kit offers an economical means of detecting each target protein that composes the nucleosome remodeling and deacetylation complex (NuRD). The kit contains enough primary antibody to perform two western blot experiments with each primary antibody.
The One-Carbon Metabolism Antibody Sampler Kit provides an economical means of detecting select components involved in one-carbon metabolism pathway. The kit contains enough primary antibodies to perform at least two western blot experiments per antibody.

Background: One-carbon metabolism includes various enzymatic reactions involving the transfer of one-carbon groups mediated by folate cofactor (1). The activated one-carbon groups are used by various metabolic pathways, including purine synthesis, thymidine synthesis, and remethylation of homocysteine to methionine (1). S-adenosylhomocysteine hydrolase-like protein 1 (AHCYL1) is a member of the S-adenosylhomocysteine hydrolase family, which participates in the metabolism of S-adenosyl-L-homocysteine (2). Cystathionine beta-synthase (CBS) is a key enzyme involved in sulfur amino acid metabolism as it catalyzes the formation of cystathionine from serine and homocysteine (3,4). Cystathionine γ-lyase (CGL) is an enzyme in the transsulfuration pathway, a route in the metabolism of sulfur-containing amino acids (5). Methylenetetrahydrofolate reductase (MTHFR), a key enzyme in one-carbon metabolism, catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate (1). 5-methyltetrahydrofolate donates its methyl group for remethylation of homocysteine to methionine (1). Methionine is further converted to S-adenosylmethionine (SAM), a major reactive methyl carrier (1). NADP+ dependent methylenetetrahydrofolate dehydrogenase 1-like (MTHFD1L) is a mitochondrial enzyme that catalyzes the production of formate from 10-formyl-tetrahydrofolate in one-carbon flow from mitochondria to cytoplasm (6,7). MTHFD2 is a bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase involved in mitochondrial folate metabolism (8). Serine hydroxymethyltransferase 1 (SHMT1) is a cytoplasmic serine hydroxylmethyltransferase (9,10). It catalyzes the conversion of serine to glycine with the transfer of β-carbon from serine to tetrahydrofolate (THF) to form 5, 10-methylene-THF (9, 10). The methylation of deoxyuridine monophosphate (dUMP) to deoxythymidine monophosphate (dTMP) is an essential step in the formation of thymine nucleotides, a process catalyzed by thymidylate synthase (TS or TYMS) (11-13).

The Organelle Localization IF Antibody Sampler Kit provides an economical means for identification of cellular organelles by fluorescence immunocytochemistry (IF-IC). This kit includes enough primary antibody to perform at least twenty IF-IC tests or two western blots with each antibody.
$320
100 µg
This peptide is used to block p21 Waf1/Cip1 (12D1) Rabbit mAb #2947 reactivity in dot blot protocols.
APPLICATIONS
REACTIVITY
Human

Application Methods: Immunohistochemistry (Paraffin)

Background: The tumor suppressor protein p21 Waf1/Cip1 acts as an inhibitor of cell cycle progression. It functions in stoichiometric relationships forming heterotrimeric complexes with cyclins and cyclin-dependent kinases. In association with CDK2 complexes, it serves to inhibit kinase activity and block progression through G1/S (1). However, p21 may also enhance assembly and activity in complexes of CDK4 or CDK6 and cyclin D (2). The carboxy-terminal region of p21 is sufficient to bind and inhibit PCNA, a subunit of DNA polymerase, and may coordinate DNA replication with cell cycle progression (3). Upon UV damage or during cell cycle stages when cdc2/cyclin B or CDK2/cyclin A are active, p53 is phosphorylated and upregulates p21 transcription via a p53-responsive element (4). Protein levels of p21 are downregulated through ubiquitination and proteasomal degradation (5).

The p38 MAPK Isoform Activation Antibody Sampler Kit provides an economical means to evaluate the activation status of individual isoforms of p38 MAPK through immunoprecipitation of the phosphorylated p38 MAPK followed by western blot using isoform specific antibodies. The kit includes enough primary and secondary antibodies to perform two IP/western blot experiments.

Background: p38 MAP kinase (MAPK), also called RK (1) or CSBP (2), is the mammalian orthologue of the yeast HOG kinase that participates in a signaling cascade controlling cellular responses to cytokines and stress (1-4). Four isoforms of p38 MAPK, p38α, β, γ (also known as Erk6 or SAPK3), and δ (also known as SAPK4) have been identified. Similar to the SAPK/JNK pathway, p38 MAPK is activated by a variety of cellular stresses including osmotic shock, inflammatory cytokines, lipopolysaccharide (LPS), UV light, and growth factors (1-5). MKK3, MKK6, and SEK activate p38 MAPK by phosphorylation at Thr180 and Tyr182. Activated p38 MAPK has been shown to phosphorylate and activate MAPKAP kinase 2 (3) and to phosphorylate the transcription factors ATF-2 (5), Max (6), and MEF2 (5-8). SB203580 (4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-imidazole) is a selective inhibitor of p38 MAPK. This compound inhibits the activation of MAPKAPK-2 by p38 MAPK and subsequent phosphorylation of HSP27 (9). SB203580 inhibits p38 MAPK catalytic activity by binding to the ATP-binding pocket, but does not inhibit phosphorylation of p38 MAPK by upstream kinases (10).

$320
100 µg
This peptide is used to block p44/42 MAPK (Erk1/2) (137F5) Rabbit mAb #4695 reactivity.
APPLICATIONS

Application Methods: Immunohistochemistry (Paraffin)

Background: Mitogen-activated protein kinases (MAPKs) are a widely conserved family of serine/threonine protein kinases involved in many cellular programs, such as cell proliferation, differentiation, motility, and death. The p44/42 MAPK (Erk1/2) signaling pathway can be activated in response to a diverse range of extracellular stimuli including mitogens, growth factors, and cytokines (1-3), and research investigators consider it an important target in the diagnosis and treatment of cancer (4). Upon stimulation, a sequential three-part protein kinase cascade is initiated, consisting of a MAP kinase kinase kinase (MAPKKK or MAP3K), a MAP kinase kinase (MAPKK or MAP2K), and a MAP kinase (MAPK). Multiple p44/42 MAP3Ks have been identified, including members of the Raf family, as well as Mos and Tpl2/COT. MEK1 and MEK2 are the primary MAPKKs in this pathway (5,6). MEK1 and MEK2 activate p44 and p42 through phosphorylation of activation loop residues Thr202/Tyr204 and Thr185/Tyr187, respectively. Several downstream targets of p44/42 have been identified, including p90RSK (7) and the transcription factor Elk-1 (8,9). p44/42 are negatively regulated by a family of dual-specificity (Thr/Tyr) MAPK phosphatases, known as DUSPs or MKPs (10), along with MEK inhibitors, such as U0126 and PD98059.