The Yeast Carboxyl-Terminal Repeat Domain Kinase CTDK-I Is a Divergent Cyclin–Cyclin-Dependent Kinase Complex

Sterner, David E.; Kim, Jae Pil; Hardin, Steven E.; Greenleaf, Andarno L.

doi:10.1128/mcb.15.10.5716

Cited by 130 publications

(121 citation statements)

References 61 publications

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“…The S. cerevisiae CTDK-I complex is encoded by three genes: CTK1, encoding a CDK subunit; CTK2, encoding a C-type cyclin subunit; and CTK3, encoding a subunit of unknown function. Disruption of any of these genes generates viable cells that display similar growth defects and are unable to grow at low temperatures (56). Cell cycle cyclins expression is tightly regulated at the level of both transcription and protein stability (43).…”

Section: Resultsmentioning

confidence: 99%

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The Yeast C-Type Cyclin Ctk2p Is Phosphorylated and Rapidly Degraded by the Ubiquitin-Proteasome Pathway

Hautbergue

Goguel

1999

Molecular and Cellular Biology

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The yeast CTDK-I complex has been implicated in phosphorylation of the carboxy-terminal domain of the RNA polymerase II and in transcription control. It is composed of three polypeptides: Ctk1p and Ctk2p, a cyclin-dependent kinase and a C-type cyclin subunit, respectively; and Ctk3p, a third subunit of unknown function. Cyclins are regulatory proteins whose expression is tightly controlled at the protein level. In this study, we examined the regulation of Ctk2p expression in vivo. Surprisingly, unlike what has been described for cell cycle cyclins, steady-state levels of Ctk2p are composed of two relatively abundant forms, one of them phosphorylated. We show that this phosphorylated form is extremely unstable (half-life, 5 min) and that rapid proteolysis of Ctk2p exhibits growth-related regulation. Furthermore, our data establish that similar to the case for other naturally short-lived proteins, Ctk2p degradation is mediated by the ubiquitin-proteasome pathway. This is the first demonstration that a C-type cyclin is phosphorylated and targeted to the proteasome. Strikingly, neither phosphorylation nor destruction of Ctk2p requires its associated kinase Ctk1p, a feature fundamentally different from that which has been observed for cell cycle cyclins.Cyclin-dependent protein kinases (CDKs) were first identified as central regulators of the major transitions of the eukaryotic cell division cycle. Their activity is determined by cyclin binding, by both positive and negative regulatory phosphorylation, and by polypeptide CDK inhibitors (40, 41). A single cyclin-dependent kinase subunit associates sequentially with multiple cyclin partners whose abundance fluctuates during the cell cycle (43). Indeed, one aspect of CDK regulation is triggered by the rapid destruction of their cyclin partners (23). Several studies both in yeast and in mammals have demonstrated that cyclins are selectively degraded by the ubiquitindependent proteasome pathway (9,16,53,67). Substrates are first marked for degradation by conjugation with several molecules of ubiquitin, a highly conserved 76-amino-acid-long polypeptide that is joined reversibly by a covalent linkage.

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Section: Resultsmentioning

confidence: 99%

“…It is composed of three subunits: the CTK1 and CTK2 genes encode a kinase and a C-type cyclin, respectively; the third subunit, Ctk3p, shows no similarity to other known proteins (30,56). Deletion of any of the CTK genes generates cryosensitive cells.…”

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confidence: 99%

The Yeast C-Type Cyclin Ctk2p Is Phosphorylated and Rapidly Degraded by the Ubiquitin-Proteasome Pathway

Hautbergue

Goguel

1999

Molecular and Cellular Biology

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“…An extant yeast extract (40) was first fractionated on a cation-exchange HiTrap S column (method 1). Bound proteins were eluted with increasing salt, subjected to SDS-PAGE, and visualized by Coomassie staining (Figure 2A).…”

Section: (A) Methods 1 Andmentioning

confidence: 99%

Expanding the Functional Repertoire of CTD Kinase I and RNA Polymerase II: Novel PhosphoCTD-Associating Proteins in the Yeast Proteome

2004

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CTD kinase I (CTDK-I) of Saccharomyces cerevisiae is required for normal phosphorylation of the C-terminal repeat domain (CTD) on elongating RNA polymerase II. To elucidate cellular roles played by this kinase and the hyperphosphorylated CTD (phosphoCTD) it generates, we systematically searched yeast extracts for proteins that bound to the phosphoCTD made by CTDK-I in vitro. Initially, using a combination of far-western blotting and phosphoCTD affinity chromatography, we discovered a set of novel phosphoCTD-associating proteins (PCAPs) implicated in a variety of nuclear functions. We identified the phosphoCTD-interacting domains of a number of these PCAPs, and in several test cases (namely, Set2, Ssd1, and Hrr25) adduced evidence that phosphoCTD binding is functionally important in vivo. Employing surface plasmon resonance (BIACORE) analysis, we found that recombinant versions of these and other PCAPs bind preferentially to CTD repeat peptides carrying SerPO 4 residues at positions 2 and 5 of each seven amino acid repeat, consistent with the positional specificity of CTDK-I in vitro [Jones, J. C., et al. (2004) J. Biol. Chem. 279, 24957-24964]. Subsequently, we used a synthetic CTD peptide with three doubly phosphorylated repeats (2,5P) as an affinity matrix, greatly expanding our search for PCAPs. This resulted in identification of approximately 100 PCAPs and associated proteins representing a wide range of functions (e.g., transcription, RNA processing, chromatin structure, DNA metabolism, protein synthesis and turnover, RNA degradation, snRNA modification, and snoRNP biogenesis). The varied nature of these PCAPs and associated proteins points to an unexpectedly diverse set of connections between Pol II elongation and other processes, conceptually expanding the role played by CTD phosphorylation in functional organization of the nucleus.The carboxyl-terminal repeat domain (CTD) 1 of the largest subunit of eukaryotic RNA polymerase II (Pol II) comprises tandem repeats of the consensus heptapeptide YSPTSPS. This highly conserved sequence, which is repeated 26 times in yeast and 52 times in mammals, is essential for viability. Phosphorylation of the CTD regulates the activities of the polymerase: only Pol II with an unphosphorylated CTD (Pol IIA) is thought to be able to assemble into preinitiation complexes at the promoter, whereas elongating polymerase has a hyperphosphorylated CTD (Pol IIO) (1,2). The serines at positions 2 and 5 within the heptad repeat represent major sites of phosphorylation during transcription. † Supported by National Institutes of Health Grant GM40505.© 2004 American Chemical Society * To whom correspondence should be addressed. . E-mail: arno@biochem.duke.edu. 1 Abbreviations: CTDK-I, CTD kinase I; Pol II, RNA polymerase II; CTD, C-terminal repeat domain; phosphoCTD, hyperphosphorylated CTD; PCTD, phosphoCTD; PCAP, phosphoCTD-associating protein; PCID, phosphoCTD-interacting domain; SGD, Saccharomyces Genome Database; SPR, surface plasmon resonance; RU, response units. NIH Publi...

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“…2B). Pch1 is more distantly related to human cyclin H (52), S. cerevisiae Srb11 (31, 33), S. pombe Mcs2 (18), S. cerevisiae Ccl1 (53), and S. cerevisiae Ctk2 (38) in which the sequence identity ranges from 17-24% (Table I). These cyclin C family members have been implicated in the regulation of RNA polymerase II transcription and in the activating phosphorylation of cyclin-dependent kinases.…”

Section: Resultsmentioning

confidence: 99%

“…Loss of Kin28 activity results in a decrease in the abundance of all mRNA species, suggesting that Kin28 kinase activity is essential for all transcription catalyzed by RNA polymerase II (37). Recently, a gene expressing the C-type cyclin subunit of a CTDK1 (CTD kinase) activity, CTK2, was cloned in S. cerevisiae (38). This cyclin-kinase pair, Ctk2-Ctk1, co-purifies with CTDK1 activity, although the in vivo role of this kinase in transcription is unknown.…”

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confidence: 99%

pch1 +, a Second Essential C-type Cyclin Gene in Schizosaccharomyces pombe

Furnari

Russell

Leatherwood³

1997

Journal of Biological Chemistry

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The Schizosaccharomyces pombe gene pch1 ؉ (pombe cyclin C homology) was isolated in a two-hybrid screen for proteins that interact with Cdc2. The cyclin box region of Pch1 protein shares greatest sequence identity with mammalian and Drosophila C-type cyclins (ϳ33% identity). Pch1 is significantly less similar to Mcs2 (19% identity), a second member of the C-type cyclin family in S. pombe. Cdc2 co-precipitates with Pch1 in S. pombe cell lysates, although Cdc2 may not be the major catalytic partner of a Pch1 kinase in vivo. Purified Pch1-associated kinase phosphorylated myelin basic protein, histone H1, and a peptide corresponding to the carboxyl-terminal domain repeat of RNA polymerase II. The amount of pch1 mRNA does not oscillate during the cell cycle, as is the case for mRNA transcripts of other C-type cyclin genes. ⌬pch1 cells are inviable, therefore S. pombe has two essential genes that encode members of the C-type cyclin family, pch1 ؉ and mcs2 ؉ . The ⌬pch1 mutation causes pleiotropic morphological defects and an associated growth deficiency, but loss of Pch1 activity does not result in a cdc cell cycle-arrest phenotype.

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The Yeast Carboxyl-Terminal Repeat Domain Kinase CTDK-I Is a Divergent Cyclin–Cyclin-Dependent Kinase Complex

Cited by 130 publications

References 61 publications

The Yeast C-Type Cyclin Ctk2p Is Phosphorylated and Rapidly Degraded by the Ubiquitin-Proteasome Pathway

The Yeast C-Type Cyclin Ctk2p Is Phosphorylated and Rapidly Degraded by the Ubiquitin-Proteasome Pathway

Expanding the Functional Repertoire of CTD Kinase I and RNA Polymerase II: Novel PhosphoCTD-Associating Proteins in the Yeast Proteome

pch1 +, a Second Essential C-type Cyclin Gene in Schizosaccharomyces pombe

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