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Human homolog of fission yeast cdc25 mitotic inducer is predominantly expressed in G2.

ABSTRACT: Entry into mitosis during the somatic cell cycle is regulated in response to signals that monitor the completion of DNA replication, the integrity of the nuclear genome, and, possibly, the increase in cellular mass during the cell cycle. It has been postulated that the operation of this cell cycle control involves the gradual accumulation of rate-limiting mitotic inducers, which trigger nuclear division when their cellular concentration reaches a critical level. We have cloned a human gene, which we call CDC25, whose product may function as a mitotic inducer. This human gene encodes a protein with a predicted molecular mass of 53,000 daltons whose C-terminal domain shares about 37% sequence identity with the fission yeast cdc25+ mitotic inducer. The human CDC25 gene rescues the defect of a fission yeast temperature-sensitive (ts) cdc25ts mutant that is unable to initiate mitosis. In HeLa cells CDC25 mRNA levels are very low in G1 and increase at least 4-fold as cells progress towards M phase. These data suggest that in human cells, as in fission yeast, the accumulation of CDC25 mitotic inducer during G2 may play a key role in regulating the timing of mitosis.

SUBMITTER: Sadhu K

PROVIDER: S-EPMC54277 | biostudies-other | 1990 Jul

REPOSITORIES: biostudies-other

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Human homolog of fission yeast cdc25 mitotic inducer is predominantly expressed in G2.

Sadhu K K Reed S I SI Richardson H H Russell P P

Proceedings of the National Academy of Sciences of the United States of America 19900701 13

Entry into mitosis during the somatic cell cycle is regulated in response to signals that monitor the completion of DNA replication, the integrity of the nuclear genome, and, possibly, the increase in cellular mass during the cell cycle. It has been postulated that the operation of this cell cycle control involves the gradual accumulation of rate-limiting mitotic inducers, which trigger nuclear division when their cellular concentration reaches a critical level. We have cloned a human gene, whic ...[more]

PMID: 2195549

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Project description:BackgroundEntry into mitosis is regulated by cyclin dependent kinases that in turn are phosphoregulated. In most eukaryotes, phosphoregulation is through WEE1 kinase and CDC25 phosphatase. In higher plants a homologous CDC25 gene is unconfirmed and hence the mitotic inducer Schizosaccharomyces pombe (Sp) cdc25 has been used as a tool in transgenic plants to probe cell cycle function. Expression of Spcdc25 in tobacco BY-2 cells accelerates entry into mitosis and depletes cytokinins; in whole plants it stimulates lateral root production. Here we show, for the first time, that alterations to cytokinin and ethylene signaling explain the rooting phenotype elicited by Spcdc25 expression in Arabidopsis.ResultsExpressing Spcdc25 in Arabidopsis results in increased formation of lateral and adventitious roots, a reduction of primary root width and more isodiametric cells in the root apical meristem (RAM) compared with wild type. Furthermore it stimulates root morphogenesis from hypocotyls when cultured on two way grids of increasing auxin and cytokinin concentrations. Microarray analysis of seedling roots expressing Spcdc25 reveals that expression of 167 genes is changed by > 2-fold. As well as genes related to stress responses and defence, these include 19 genes related to transcriptional regulation and signaling. Amongst these was the up-regulation of genes associated with ethylene synthesis and signaling. Seedlings expressing Spcdc25 produced 2-fold more ethylene than WT and exhibited a significant reduction in hypocotyl length both in darkness or when exposed to 10 ppm ethylene. Furthermore in Spcdc25 expressing plants, the cytokinin receptor AHK3 was down-regulated, and endogenous levels of iPA were reduced whereas endogeous IAA concentrations in the roots increased.ConclusionsWe suggest that the reduction in root width and change to a more isodiametric cell phenotype in the RAM in Spcdc25 expressing plants is a response to ethylene over-production. The increased rooting phenotype in Spcdc25 expressing plants is due to an increase in the ratio of endogenous auxin to cytokinin that is known to stimulate an increased rate of lateral root production. Overall, our data reveal important cross talk between cell division and plant growth regulators leading to developmental changes.

Dataset Information

Human homolog of fission yeast cdc25 mitotic inducer is predominantly expressed in G2.

Publications

Human homolog of fission yeast cdc25 mitotic inducer is predominantly expressed in G2.

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