Characterization of the 3 ' untranslated region of mouse E2F1 mRNA

The E2F family of transcription factors has been implicated in the regulati on of the G1 to S phase transition of the mammalian cell cycle. We have foc used on characterizing the cell cycle stage-specific expression of one fami ly member, E2F1. Previous studies indicated that there are two mouse E2F1 ( mE2F1) mRNA species whose abundance peaks in early S phase. However, it was unknown as to what constituted the structural difference between the two m E2F1 mRNAs and whether or not they encoded identical proteins. We have now cloned sequences corresponding to the 3' untranslated region (3'-UTR) of th e mE2F1 gene. Northern blot analyses using different probes demonstrated th at the two E2F1 mRNAs were distinguished by differences in the length of th eir 3' UTRs. We found that the longer (2.7-kb) mE2F1 mRNA contained two con sensus RNA instability elements that the shorter (2.2-kb) mE2F1 mRNA lacked . However, a comparison of the stability of the 2.7-kb and the 2.2-kb mE2F1 mRNAs suggests that both mE2F1 mRNAs are fairly stable, having a half-life of 6-9 h in both asynchronously growing cells and in the S phase of synchr onized cells. Thus, we have determined that both mE2F1 mRNAs contain the id entical coding region of the E2F1 protein and that enforced expression of m E2F1 mRNA should not be hampered by problems with RNA stability. (C) 1998 E lsevier Science B.V. All rights reserved.