Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using subtraction cloning, we have isolated a human cDNA, AS321, which is expressed in retina and retinoblastoma cell lines but not in any other tissue or cell line tested. AS321 mRNA is detected in all cells of neural retina, with a high level of expression in photoreceptors. The polypeptide sequence deduced from the cDNA reveals consensus phosphorylation sites for protein kinase A and proline-directed protein kinase. Its C-terminal region contains a basic motif and a leucine zipper domain similar to the DNA binding proteins of the jun and fos oncoprotein family, and it shows a strong similarity to the product of an avian retroviral oncogene, v-maf. The gene for AS321 is conserved during evolution and is expressed in vertebrate retina. We propose to name the gene NRL (neural retina leucine zipper.
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PMID:A conserved retina-specific gene encodes a basic motif/leucine zipper domain. 172 96

We have studied the initial effects of adenovirus E1A expression on the retinoblastoma (RB) gene product in normal quiescent cells. Although binding of the E1A products to pRB could, in theory, make pRB phosphorylation unnecessary for cell cycle progression, we have found that the 12S wild-type E1A product is capable of inducing phosphorylation of pRB in normal quiescent cells. The induction of pRB phosphorylation correlates with E1A-mediated induction of p34cdc2 expression and kinase activity, consistent with the possibility that p34cdc2 is a pRB kinase. Expression of simian virus 40 T antigen induces similar effects. Induction of pRB phosphorylation is independent of the pRB binding activity of the E1A products; E1A domain 2 mutants do not bind detectable levels of pRB but remain competent to induce pRB phosphorylation and to activate cdc2 protein kinase expression and activity. Although the kinetics of induction are slower, domain 2 mutants induce wild-type levels of pRB phosphorylation and host cell DNA synthesis and yet fail to induce cell proliferation. These results imply that direct physical interaction between the RB and E1A products does not play a required role in the early stages of E1A-mediated cell cycle induction and that pRB phosphorylation is not, of itself, sufficient to allow quiescent cells to divide. These results suggest that the E1A products do not need to bind pRB in order to stimulate resting cells to enter the cell cycle. Indeed, a more important role of the RB binding activity of the E1A products may be to prevent dividing cells from returning to G0.
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PMID:E1A induces phosphorylation of the retinoblastoma protein independently of direct physical association between the E1A and retinoblastoma products. 183 Jan 28

In yeast G1, cyclins control the Cdc28 protein kinase in order to regulate the primary cell cycle gating event known as START. Environmental and internal signals that control the cell cycle do so, apparently, by controlling the synthesis and/or stability of G1 cyclins, hence controlling the activity of the Cdc28 kinase. The substrates of the Cdc28 kinase that are critical for passage through START are not known. One simple hypothesis is that the G1 kinase phosphorylates and thus activates a transcription factor required for the initiation of S phase. The synthesis of an origin of replication-binding factor might be regulated in this fashion. Recent evidence suggests that Cdc28 protein kinase activity directly regulates the transcription of a family of genes whose products are required for DNA replication (N. Marini and S. Reed, in prep.). However, it is not yet known whether this transcriptional activation constitutes the execution of START. The situation in animal cells is more complex. A number of new cyclins and p34s have been identified. It is not clear yet which of these, if any, have functions in G1 and if they do, what functions these might be. If G1 cyclins and p34 kinases do have critical G1 roles, by analogy with yeast, they may couple signals mediated by both positive and negative growth factors to cell cycle progression. Candidates for the critical G1 substrates of these putative G1 protein kinases are the tumor suppressors such as the RB (retinoblastoma) gene product (p105RB).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:G1 control in yeast and animal cells. 184 Feb 66

Synthetic peptides have been used to define the consensus amino acid sequence for substrate recognition by the meiosis-activated myelin basic protein (MBP) kinase (p44mpk), which was purified from maturing sea star oocytes. This protein kinase shares many properties with the mitogen-activated microtubule-associated protein-2 kinase (p42mapk) in vertebrates. Recently, Thr-97 in the tryptic fragment KNIVTPRTPPPSQGK of bovine MBP was identified as the major site of phosphorylation by p44mpk (Sanghera, J. S., Aebersold, R., Morrison, H. D., Bures, E. J., and Pelech, S. L. (1990) FEBS Lett. 273, 223-226). Synthetic peptides modeled after this sequence revealed that the presence of a proline residue C-terminal (+1 position) to the phosphorylatable threonine (or serine) residue was critical for recognition by p44mpk. Although not essential, a proline residue located at the -2 position enhanced the Vmax of peptide phosphorylation. Basic, acidic, and non-polar residues were equally tolerated at the -1 position. The presence of an amino acid residue at position -3 also increased peptide phosphorylation. Thus, the optimum consensus sequence for phosphorylation by p44mpk was defined as Pro-X-(Ser/Thr)-Pro, where X is a variable amino acid residue, but ideally not a Pro. Peptides that included this sequence were phosphorylated by p44mpk with Vmax values approaching 1 mumol.min-1.mg-1 and with apparent Km values of approximately 1 mM). Pseudosubstrate peptides in which the phosphorylatable residue was replaced by valine or alanine were weak inhibitors of p44mpk (apparent Ki values of approximately 3 mM). Over 40 distinct protein kinases contain Pro-X-(Ser/Thr)-Pro sequences including the human receptors for insulin and epidermal growth factor, and kinases encoded by the human proto-oncogenes abl, neu, and raf-1, and Schizosaccharomyces pombe cell cycle control genes ran-1 and wee-1. Multiple putative sites were also identified in rat microtubule-associated protein-2, human retinoblastoma protein, human tau protein, and Drosophila myb protein and RNA polymerase II.
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PMID:Definition of a consensus sequence for peptide substrate recognition by p44mpk, the meiosis-activated myelin basic protein kinase. 190 71

The E7 protein of human papillomavirus type 16 (HPV16) transforms cultured cells and cooperates with the ras or fos oncogenes in the transformation of primary cells. In this study we have investigated the phosphorylation of E7. When we immunoprecipitated E7 from CaSki cells with a rabbit polyclonal antiserum to a bacterial fusion protein (trpE-E7), we found that E7 was phosphorylated at serine residues contained in five characteristic thermolysin peptides. Immunoprecipitated E7, and fusion proteins harboring the E7 protein from various HPV types, could all be specifically phosphorylated in vitro by the ubiquitous, growth factor-activated casein kinase II (CKII). Comparative peptide mapping showed that the sites of in vivo and in vitro phosphorylation are the same. CKII was shown previously to specifically phosphorylate serine or threonine residues within a cluster of acidic amino acids. The E7 protein contains such a sequence between amino acids 30 and 37. When a synthetic peptide corresponding to this region of E7 was phosphorylated by CKII in vitro, its thermolysin digestion products were the same as those in the phosphorylated E7 protein. We conclude that E7 is phosphorylated in vivo only at serines within the predicted CKII site and that CKII, or a CKII-like enzyme, participates in the reaction. Both the E1A and SV40 large T proteins contain similar CKII consensus sites proximal to the regions required for their associations with the retinoblastoma gene product (p105Rb). Thus it is conceivable that CKII phosphorylation can modulate the interaction between the transforming proteins and the retinoblastoma gene product.
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PMID:The E7 protein of human papillomavirus type 16 is phosphorylated by casein kinase II. 256 89

An indirect immunofluorescence technique was employed to determine the intracellular distribution of the regulatory subunit of type II cyclic adenosine 3':5'-monophosphate-dependent protein kinase (RII) in Y-79 human retinoblastoma cells growing in monolayer culture. During the initial phases of growth (6 hr-6 days after seeding), RII was confined to the cytoplasmic areas of the Y-79 cells, seemingly, the Golgi apparatus. Treatment of cells for 3-5 days with 4 mM butyrate resulted in translocation of RII from cytoplasm to nuclei (mainly nucleoli) of cells. In a later stage of growth (24-day-old cultures), RII immunofluorescence was significantly decreased in all compartments within the untreated cells. In contrast, about 70% of the butyrate-treated cells yet showed nucleoli and/or cytoplasmic localization of RII at this stage. The nucleolar appearance of RII was parallel to the growth arrest and differentiation induced by butyrate.
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PMID:Distribution of the regulatory subunit of type II cAMP-dependent protein kinase in Y-79 retinoblastoma cells. Effect of butyrate. 352 34

Studies on the molecular mechanisms underlying neuronal differentiation are frequently performed using cell lines established from neuroblastomas. In this study we have used mouse N1E-115 neuroblastoma cells that undergo neuronal differentiation in response to DMSO. During differentiation, cyclin-dependent kinase (cdk) activities decline and phosphorylation of the retinoblastoma gene product (pRb) is lost, leading to the appearance of a pRb-containing E2F DNA-binding complex. The loss of cdk2 activity is due to a decrease in cdk2 abundance whereas loss of cdk4 activity is caused by strong association with the cdk inhibitor (CKI) p27KIP1 and concurrent loss of cdk4 phosphorylation. Moreover, neuronal differentiation can be induced by overexpression of p27KIP1 or pRb, suggesting that inhibition of cdk activity leading to loss of pRb phosphorylation, is the major determinant for neuronal differentiation.
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PMID:Inhibition of cyclin-dependent kinase activity triggers neuronal differentiation of mouse neuroblastoma cells. 755 79

Aberrant cyclin expression has been implicated in oncogenesis in a number of human cancers. Since altered function of regulators of cyclin-dependent kinase (CDK) activity other than cyclins, in particular CDK inhibitors, might play a similar role in oncogenesis, we examined the expression and regulation of the CDK inhibitors p16INK4, p15INK4B and p21WAF1/CIP1 in human breast cancer cell lines. Both the INK4 and INK4B genes were homozygously deleted in 3 cell lines, while INK4 alone was deleted in 2 cell lines. A further 2 cell lines displayed loss of an allele at this locus, and in 1 of these the remaining allele contained a mis-sense mutation within the coding region of the p16INK4 protein. The majority of cell lines examined, including 2 normal mammary epithelial cell strains, expressed low levels of INK4 mRNA and low or undetectable levels of INK4B mRNA. However, INK4 mRNA was expressed at high levels in 5 cell lines, and this was associated with deletion or inactivation of the retinoblastoma susceptibility gene product pRB but not with mutation of TP53. No deletions of the WAF1/CIP1 gene were observed, but WAF1/CIP1 mRNA levels were reduced in cell lines with TP53 mutation. Transfection of a p16INK4 expression vector into MDA-MB-231 cells lacking the INK4 gene failed to produce any p16INK4-expressing cell lines, suggesting that such cells were selected against in continuous culture. Despite the frequent deletion of INK4 in breast cancer cell lines, no evidence was obtained for INK4 deletions in DNA from 45 primary breast carcinomas. Thus, homozygous deletion of the INK4 gene appears to be a rare event in primary breast cancer.
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PMID:Expression of the cyclin-dependent kinase inhibitors p16INK4, p15INK4B and p21WAF1/CIP1 in human breast cancer. 759 Dec 70

We have previously demonstrated that cells from patients with ataxia-telangiectasia (A-T) fail to show initial delay at several cell cycle checkpoints post-irradiation. In addition a defect in the induction of p53 by ionizing radiation was evident. We demonstrate here that the radiation signal transduction pathway operating through p53, its target gene WAF1, cyclin-dependent kinases and the retinoblastoma (Rb) protein is defective in A-T cells. The defective p53 induction after ionizing radiation, observed previously in A-T cells, was also reflected at the functional level using p53-DNA binding activity, transactivation and transfection with wild type p53. Correction of the defect at the G1/S checkpoint was observed when wild type p53 was constitutively expressed in A-T cells. Exposure of control cells to radiation gave rise to p53 induction and as a consequence increased expression of WAF1 mRNA and protein, but A-T cells were defective in this response. As expected the WAF1 response in irradiated control cells resulted in an inhibition of cyclin-dependent kinase activity including cyclin E-cdk2, which plays an important role in the transition from G1 to S phase. No inhibition of cyclin-dependent kinase activity was observed in A-T cells correlating with the delayed WAF1 response. On the contrary an enhancement of cyclin-dependent kinase activity was seen in A-T cells post-irradiation. An accumulation of the hypophosphorylated form of Rb protein occurred in irradiated control cells compatible with the G1/S phase delay observed in these cells after exposure to radiation. In unirradiated A-T cells the amount of Rb protein was much higher compared to controls and it was mainly in the hyperphosphorylated (functionally inactive) form. In addition, accumulation of the hypophosphorylated form of Rb in A-T cells post-irradiation was defective, consistent with the lack of cell cycle arrest. Thus the failure of the G1/S checkpoint in A-T cells after exposure to ionizing radiation is consistent with a defective radiation signal transduction pathway operating through p53.
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PMID:Nature of G1/S cell cycle checkpoint defect in ataxia-telangiectasia. 765 23

The cyclin-dependent kinase inhibitors p16INK4/MTS1 and p15INK4B/MTS2 have been mapped to a region in chromosome 9 (921) that is deleted frequently in acute lymphoblastic leukemias and malignant gliomas. To gain insight into the functions of these inhibitors in lymphocytes and neuronal cells, we studied the expression of p15 and p16 during lymphocyte mitogenesis and neuronal differentiation. Expression of p15 was extinguished during lymphocyte activation, concomitant with an increase in retinoblastoma kinase activity. The differentiation of the embryonic teratocarcinoma cell line NT2 into postmitotic neurons (hNT) was associated with enhanced expression of p15 and p16 proteins. These findings suggest that p15 and p16 play a role in maintaining cell quiescence in lymphocytes and neuronal cells, respectively. Deletions of these genes may thus promote unrestrained growth.
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PMID:Expression of the p16 and p15 cyclin-dependent kinase inhibitors in lymphocyte activation and neuronal differentiation. 766 73


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