Chromosome 6 encoded RNaseT2 protein is a cell growth regulator

We have previously shown by chromosome transfer technique that chromosome 6 alters the phenotype of a variety of tumour cells and SV40 immortalized cells. We present here the phenotypic effects of the ectopic expression of RNaseT2, a highly conserved ribonuclease encoded by chromosome 6q27, in SV40 immortalized cell lines. We contrast our findings with those reported for ovarian carcinoma cell lines and an SV40 immortalized cell line transfected with RNaseT2. Although RNaseT2 expression is elevated in normal diploid fibroblasts approaching senescence (passage 64), forced expression of the gene in immortalized cells does not cause them to senesce. A significant reduction was observed in colony forming efficiency, anchorage independence and growth rate of cells transfected with RNaseT2. The levels of transcripts involved in Akt signalling pathway, cell cycle control and pathways related to cell proliferation decreased 2-10-folds in SV40 immortalized cells in response to RNaseT2 expression. Interestingly, some immortalized cells expressed alternatively spliced transcript variants instead of the full-length RNaseT2 transcript. Our results are consistent with the conclusion that RNaseT2 is a cell growth regulator and it does not induce senescence in SV40 immortalized cell lines.