Translation of unspliced transcripts after heat shock.

Severe heat shocks block the splicing of intervening sequences from messenger RNA precursors. The RNA's that accumulate after a severe heat shock have normal transcription start sites and are uncut at both their 5' and 3' splice junctions. Some of these unspliced transcripts leave the nucleus and enter the pool of cytoplasmic messenger RNA. Translation of these RNA's proceeds into their intervening sequences, resulting in the production of abnormal proteins. Thus, the repression of normal transcription, which usually accompanies the heat shock response, may protect the cell from the large-scale synthesis of abnormal RNA's and aberrant proteins.