Isolation of a novel cDNA whose corresponding mRNA is accumulated in growth-arrested confluent but not in growing sub-confluent rat 3Y1 cells.

Four cDNA fragments, whose corresponding mRNAs were accumulated in growth-arrested confluent but not in growing sub-confluent rat 3Y1 cells, were isolated by the mRNA differential display method. Sequencing of the four cDNA fragments indicated that one of them was highly homologous to 3' untranslated DNA region of mouse growth-arrest specific1 cDNA, while the other three (named confluent 3Y1 cell-associated No. 1 (cca1), cca2 and cca3) were novel. Of the three novel cDNAs, we presented some characteristics of cca2 cDNA: the cDNA consisted of 1795 nucleotides with a deduced open reading frame (ORF) encoding a protein of 338 amino acids, which showed a 35% identity with rat type IV 3beta-hydroxysteroid dehydrogenase. The CCA2 protein, with a molecular weight of 38 kDa, was accumulated in 3Y1 cells under growth-arrest conditions.