Characterization of cDNAs encoding the murine A + U-rich RNA-binding protein AUF1

A + U-rich elements (ARE) serve to control the degradation of some proto-oncogene and lymphokine mRNAs. The protein, AUF1, which consists of two polypeptides of 37 and 40 kDa (p37 and p40, respectively) when purified from cytosol, has been implicated in ARE-directed mRNA turnover due to its binding to ARE. Molecular cloning of a cDNA (p37^AUF1) corresponding to human p37 predicted a polypeptide containing two non-identical RNA recognition motifs (RRM) and a C-terminal Gin-rich domain [Zhang et al. Mol. Cell. Biol. 13 (1993) 7652-7665]. Two cDNAs, designated mu AUF1-3 and muAUF1-7, were isolated from a murine fetal cDNA library, using as a probe, a fragment of the p37^AUF1 cDNA encoding RRM1 and approximately half of RRM2. The muAUFl-3 open reading frame (ORF) was very homologous to human p37^AVF1 with the greatest homology between the corresponding RRMs and the C-terminal Gin-rich motif. Clone muAUFl-7 was highly homologous to muAUFl-3, but was truncated within the region encoding the RNP-1 box in RRM2. Clone muAUFl-3 encoded 19 amino acids in RRM1 not encoded by either muAUFl-7 or human p37^AUF1. Such alterations in sequence could modify the RNA-binding properties of these proteins and have concomitant effects on ARE-directed posttranscriptional processes.