Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protein Phosphatase-1 is phosphorylated in vitro by cdc2-cyclin B (Villa-Moruzzi, FEBS Lett 304: 211-215, 1992). In the present study we show that all the three Phosphatase-1 isoforms, alpha, gamma 1, delta, are phosphorylated by cdc2-cyclin B. Phosphorylation is specific for this kinase and involves a C-terminal Thr. This site is most likely Thr 320 in alpha (shown by others to be phosphorylated also by cdc2-cyclin A). Such Thr is conserved in gamma 1, delta and in the testis-specific gamma 2, and is the only Thr that fits the cdc2-consensus sequence in the C-terminal region. Phosphorylation of Phosphatase-1 purified from skeletal muscle, which is a mixture of the alpha, gamma 1 and delta isoforms, is up to 0.4 mol/mol and induces 30-35% enzyme inactivation. Following tryptic proteolysis each isoform yields a distinct phosphopeptide map. This is in agreement with the different sequences of the isoforms in the C-terminal regions and may be useful to distinguish the isoforms in extracts from metabolically-labelled cells. Our results suggest that all the Phosphatase-1 isoforms may be potentially regulated at M-phase.
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PMID:Phosphorylation of protein phosphatase-1 isoforms by cdc2-cyclin B in vitro. 920 3

A 1933 bp cDNA fragment, coding a truncated testis-specific novel nucleoporin, was isolated from a human testis lambdaZAPII cDNA library, designated as BS-63 and assigned GenBank accession number: U64675. By applying the methods of rapid amplification of cDNA ends (5' RACE) and PCR, a full-length BS-63 cDNA composed of 5475 bp was obtained. BS-63 cDNA contained an open reading frame consisting of 1765 codons and XFXFG or GLFG repetitive sequence motifs. These repetitive motifs are structural characteristic of nucleoporins. BS-63 cDNA has high homology with Nup358/Ran BP2. A 1599 bp fragment, corresponding to the C-terminus of BS-63 cDNA, was prepared and expressed in E. coli BL21(DE3). The recombinant product was purified by affinity chromatography and SDS-PAGE and polyclonal antibodies raised. In rat testis section, the BS-63 protein was localized at the sites of nuclear pores in spermatids by immuno-gold transmission electron microscopy and on the nuclear membrane of Triton X-treated sperm by colloidal silver immuno-gold scanning electron microscopy. The recombinant BS-63 protein can be phosphorylated in vitro with PKC and p34(cdc2). A yeast two-hybrid system was used to screen a mouse testis cDNA library to identify proteins capable of interacting with BS-63. Using the 1.6 kb cDNA fragment as bait, the following interacting proteins were identified: Ran, transportin (karyopherin beta2), two proteins related to the nucleocytoplasmic transporter and aF10 protein. The latter protein is a putative transcriptor containing a cysteine-rich N-terminus, a LAP/PHD finger, a leucine zipper domain and a glutamine-rich C-terminus. Also it is highly expressed in murine testis and is located in the cell nucleus and cytoplasm. The interaction of BS-63 with aF10 (696-1001aa) was validated by surface plasmon resonance and by affinity precipitation combined with Western blot. aF10 (696-1001aa) interacted in vitro with BS-63 extracted from rat testis germ cells. It is hypothesized that BS-63 is a testis-specific nucleoporin and possibly acts as a docking site and a cotransporter of Ran and transportin. The complex performs the task of a carrier system in transporting aF10 into the nucleus of germ cells during spermiogenesis.
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PMID:Characterization and potential function of a novel testis-specific nucleoporin BS-63. 1177 84

In addition to their activation via binding to cyclins, cyclin-dependent kinases (CDKs) can be activated via binding to a novel cell cycle regulator termed Speedy/Ringo, which shows no apparent similarity to cyclins. The first Speedy/Ringo protein was found to be essential for Xenopus oocyte maturation and a human homolog (Spy1, herein called Speedy/ Ringo A1) regulates S-phase entry and cell survival after DNA damage in cultured somatic cells. We have identified a Speedy/Ringo-like gene in the most primitive branching clade of chordates (Ciona intestinalis), as well as four mammalian homologs. Of the mammalian proteins, two, Speedy/Ringo A and C, bind to Cdc2 and Cdk2, whereas Speedy/Ringo B binds preferentially to Cdc2. Despite their distinct CDK-binding preferences, both Speedy/Ringo A and B can promote the maturation of Xenopus oocytes and all three Speedy/Ringo proteins can bind to and activate CDKs in vivo. These mammalian Speedy/Ringo proteins exhibit distinct tissue expression patterns, though all three are enriched in testis, consistent with the initial observation that Xenopus Speedy/Ringo functions during meiosis. Speedy/Ringo A is widely expressed in tissues and cell lines. Speedy/Ringo B expression appears to be testis-specific. Speedy/Ringo C is expressed in diverse tissues, particularly those that undergo polyploidization. All Speedy/Ringo proteins share a highly conserved approximately 140-aa domain we term the Speedy/Ringo box that is essential for CDK binding. Point mutations in this domain abolish CDK binding. Besides the central Speedy/Ringo box, Speedy/Ringo A contains a C-terminal portion, which promotes CDK activation, and an N-terminal portion, which is dispersible for both CDK binding and activation but that influences protein expression. The existence of this growing family of CDK activators suggests that Speedy/Ringo proteins may play as complex a role in cell cycle control as the diverse family of cyclins.
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PMID:Identification and comparative analysis of multiple mammalian Speedy/Ringo proteins. 1561 25

Previous studies gave differing results as to whether the testis-specific histone H1t was phosphorylated during rodent spermatogenesis. We show here that histones extracted from germ cell populations enriched with spermatids at different stages of development in rat testes reveal an electrophoretic shift in the position of H1t to slower mobilities in elongating spermatids as compared to that from preceding stages. Alkaline phosphatase treatment and radioactive labeling with (32)P demonstrated that the electrophoretic shift is due to phosphorylation. Mass spectrometric analysis of histone H1t purified from sexually mature mice and rat testes confirmed the occurrence of singly, doubly, and triply phosphorylated species, with phosphorylation sites predominantly found at the C-terminal end of the molecule. Furthermore, using collision-activated dissociation (CAD) and electron transfer dissociation (ETD), we have been able to identify the major phosphorylation sites. These include a new, previously unidentified putative H1t-specific cdc2 phosphorylation site in linker histones. The presence of phosphorylation at the C-terminal end of H1t and the timing of its appearance suggest that this post-translational modification is involved in the reduction of H1t binding strength to DNA. It is proposed that this could participate in the opening of the chromatin fiber in preparation for histone displacement by transition proteins in the next phase of spermiogenesis.
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PMID:C-terminal phosphorylation of murine testis-specific histone H1t in elongating spermatids. 1869 3

During normal spermatogenesis, the testis-specific linker histone H1t appears at pachytene stage becomes phosphorylated in early spermatids and disappears in late spermatids. Using reversed-phase and hydrophilic interaction liquid chromatography, H1t from rat and mouse testes was isolated, subjected to enzymatic digestion, and analyzed by mass spectrometry. We observed different phosphorylated states of H1t (mono-, di-, and triphosphorylated) as well as the unphosphorylated protein. Tandem mass spectrometry and immobilized metal ion affinity chromatography experiments with MS/MS/MS and multistage activation were utilized to identify five phosphorylation sites on H1t from rats. Phosphorylation occurs on both serine and threonine residues, whereas only two of these sites were located on peptides containing the CDK consensus motif (S/T)PXZ. Rat H1t phosphorylation starts first by phosphorylation of the nonconsensus motif SPKS in the COOH-terminal domain, namely at Ser-140 and to a smaller degree at a further nonconsensus motif at Ser-186. This is followed by phosphorylation of Ser-177 and Thr-155, both located in CDK consensus motifs. A single phosphorylation site at Ser-8 in the NH2-terminal tail was also found. Mouse H1t lacks Ser-186 and is phosphorylated at up to four sites. In contrast to somatic linker histones, no strict order of increasing phosphorylation could be detected in H1t. Thus, it appears that not the order of up-phosphorylation but the number of the phosphate groups is necessary for regulated chromatin decondensation, thus facilitating the substitution of H1t by transition proteins and protamines.
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PMID:Testis-specific linker histone H1t is multiply phosphorylated during spermatogenesis. Identification of phosphorylation sites. 1904 17