Abstract
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 mu
AUF1-7, 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 mu
AUFl-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 mu
AUFl-7 was highly homologous to mu
AUFl-3, but was truncated within the region encoding the RNP-1 box in RRM2. Clone mu
AUFl-3 encoded 19 amino acids in RRM1 not encoded by either mu
AUFl-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.