Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.5.1.18 (glutathione S-transferase)
 22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The c-abl proto-oncogene encodes a nuclear tyrosine kinase that can phosphorylate the mammalian RNA polymerase II (RNAP II) on its C-terminal repeated domain (CTD) in vitro. Phosphorylation of the CTD has previously been shown to require the tyrosine kinase and the SH2 domain of Abl. We show here that a CTD-interacting domain (CTD-ID) at the C-terminal region of c-Abl is also required. Deletion of the CTD-ID causes the Km 0.4 microM to increase by 2 orders of magnitude. Direct binding of the CTD-ID to CTD and to RNAP II could be demonstrated in vitro. Phosphorylation of a recombinant glutathione S-transferase-CTD by c-Abl was observed in cotransfected COS cells. Mutant Abl proteins lacking the CTD-ID, while capable of autophosphorylation, neither phosphorylated nor associated with the glutathione S-transferase-CTD in vivo. Transient overexpression of c-Abl also led to a four- to fivefold increase in the phosphotyrosine content of the RNAP II large subunit. Moreover, the large subunit of RNAP II could be coprecipitated with c-Abl. Tyrosine phosphorylation of the coprecipitated RNAP II was again dependent on the presence of the CTD-ID in Abl. Finally, the ability of c-Abl to phosphorylate and associate with RNAP II could be correlated with the enhancement of transcription by c-Abl in transient cotransfection assays. Taken together, these observations demonstrate that c-Abl can function as a CTD kinase in vitro as well as in vivo.
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PMID:Identification of a binding site in c-Ab1 tyrosine kinase for the C-terminal repeated domain of RNA polymerase II. 866 51

The cotranscriptional placement of the 7-methylguanosine cap on pre-mRNA is mediated by recruitment of capping enzyme to the phosphorylated carboxy-terminal domain (CTD) of RNA polymerase II. Immunoblotting suggests that the capping enzyme guanylyltransferase (Ceg1) is stabilized in vivo by its interaction with the CTD and that serine 5, the major site of phosphorylation within the CTD heptamer consensus YSPTSPS, is particularly important. We sought to identify the CTD kinase responsible for capping enzyme targeting. The candidate kinases Kin28-Ccl1, CTDK1, and Srb10-Srb11 can each phosphorylate a glutathione S-transferase-CTD fusion protein such that capping enzyme can bind in vitro. However, kin28 mutant alleles cause reduced Ceg1 levels in vivo and exhibit genetic interactions with a mutant ceg1 allele, while srb10 or ctk1 deletions do not. Therefore, only the TFIIH-associated CTD kinase Kin28 appears necessary for proper capping enzyme targeting in vivo. Interestingly, levels of the polyadenylation factor Pta1 are also reduced in kin28 mutants, while several other polyadenylation factors remain stable. Pta1 in yeast extracts binds specifically to the phosphorylated CTD, suggesting that this interaction may mediate coupling of polyadenylation and transcription.
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PMID:Kin28, the TFIIH-associated carboxy-terminal domain kinase, facilitates the recruitment of mRNA processing machinery to RNA polymerase II. 1059 13

In Saccharomyces cerevisiae, Kin28 is a member of the cyclin-dependent kinase family. Kin28 is a subunit of the basal transcription factor holo-TFIIH and its trimeric sub-complex TFIIK. Kin28 is the primary kinase that phosphorylates the RNA polymerase II (RNA pol II) C-terminal domain (CTD) within a transcription initiation complex. Mediator, a global transcriptional co-activator, dramatically enhances the phosphorylation of the CTD of RNA pol II by holo-TFIIH in vitro. Using purified proteins we have determined that the subunits of TFIIK are sufficient for Mediator to enhance Kin28 CTD kinase activity and that Mediator enhances phosphorylation of a glutathione S-transferase-CTD fusion protein, despite the absence of multiple Mediator and/or TFIIH interactions with polymerase. Mediator does not stimulate the activity of several other CTD kinases, suggesting that the specific enhancement of TFIIH kinase activity results in Kin28 being the primary CTD kinase at initiation. In addition, we have found that Kin28 phosphorylates Mediator subunit Med4 in an assay, including purified holo-TFIIH, and either Mediator or recombinant Med4 alone. Furthermore, Kin28 appears to be, at least in part, responsible for the phosphorylation of Med4 in vivo. We have identified Thr-237 as the site of phosphorylation of Med4 by Kin28 in vitro. The mutation of Thr-237 to Ala has no effect on the growth of a yeast strain under normal conditions but confirms that Thr-237 is also the site of Med4 phosphorylation in vivo.
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PMID:Mutual targeting of mediator and the TFIIH kinase Kin28. 1512 97