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[Cloning and tissue expressive pattern analysis of the human ribosomal S6 kinase-RPS6KA5 cDNA]
Abstract:
Human ribosomal protein S6 kinase includes two protein families: P90RSK and P70S6K, they participate in two different signaling pathways. When the two kinases were inhibited by their antibodies or rapamycin, the proliferation of cells was arrested. However, their analog, the immunosupressant FK-506, can inhibit the proliferation of fibroblast PBL1 without interfering with the activities of P90RSK, P70S6K and MAPK. We take the tactics of "homolog screening" to demonstrate whether there are some novel proteins which can substitute for the known P90RSK and P70S6K or other pathways without interfering with the known P90RSK and P70S6K. With the conserved sequence of mouse p90RSK as a probe, we screened the homologous sequence in NCBI EST database and got three human EST fragments. With the assembled contig as a probe to screen human brain cDNA library, a full-length cDNA of 3833 bp was attained. It contains a completed open reading frame from 165 bp to 2570 bp encoding 802 amino acids. The putative protein has higher homology with other members of p90RSK family. The gene was named RPS6KA5, the accession number in GenBank is AF090421. Northern hybridization showed the gene expressed in 16 human tissues tested, and the gene was localized in 14q31-32.1 by RH mapping. Another novel P70S6K gene has also been cloned. Thus, our initial presumption that there is an analog of known P90RSK and P70S6K in human beings was proved.
Insights
Researchers identified a novel human gene, RPS6KA5, related to cell proliferation pathways. This discovery suggests new targets for understanding cell growth regulation beyond known P90RSK and P70S6K kinases.
Area of Science:
- Molecular Biology
- Cell Signaling
- Genetics
Context:
- Human ribosomal protein S6 kinase (RSK) encompasses P90RSK and P70S6K families involved in distinct signaling pathways.
- Inhibition of these kinases or rapamycin arrests cell proliferation.
- The immunosuppressant FK-506 inhibits fibroblast proliferation without affecting P90RSK, P70S6K, or MAPK activity, suggesting alternative regulatory mechanisms.
Purpose:
- To investigate the existence of novel proteins that could substitute for known P90RSK and P70S6K kinases or operate through alternative pathways.
- To identify new regulators of cell proliferation independent of established RSK pathways.
Summary:
- Homolog screening using mouse p90RSK sequence identified three human EST fragments.
- Assembly and screening of a human brain cDNA library yielded a full-length cDNA (3833 bp) encoding 802 amino acids, named RPS6KA5 (GenBank accession AF090421).
- RPS6KA5 exhibits homology to the p90RSK family, is expressed in 16 human tissues, and localized to chromosome 14q31-32.1. A novel P70S6K gene was also cloned.
Impact:
- Confirms the existence of novel analogs to known P90RSK and P70S6K proteins in humans.
- Provides new molecular targets for research into cell proliferation control.
- Expands understanding of the complex signaling networks regulating cell growth and division.