Cloning of murine early quiescence-1 gene: the murine counterpart of dermatopontin gene can induce and be induced by cell quiescence.

Using the method of differential display, we identified a murine gene (GenBank accession number ) specifically expressed in quiescent cells, that is, BALB/c 3T3 cells rendered quiescent by serum deprivation or by contact inhibition. The cloned promoter was 1367 bp in length (accession number ). This gene was called early quiescence-1 (EQ-1) gene because its induction could be detected within 3 h following serum deprivation. EQ-1 is markedly expressed in the heart and lung. The full-length EQ-1 cDNA, cloned from a mouse lung cDNA library, is 1673 bp in length and consists of 26 bp 5' untranslated region, 603 bp coding region, and 1044 bp 3' untranslated region, the latter of which harbors two polyadenylation signals. Because the deduced amino acid residues are of 92% homology to human dermatopontin, EQ-1 represents the murine counterpart of the human dermatopontin. The stably transfected cell line harboring EQ-1 driven by an inducible promoter showed approximately 50% inhibition on cell proliferation after being treated with an inducer for 5 days. These results suggest that the cell quiescence-induced EQ-1 gene can induce cell quiescence, implicating a self-driven mechanism of antiproliferation.