ABSTRACT
Several mRNAs have been shown to exhibit distinct patterns of poly(A) shortening prior to their decay in vivo. In this study, we show that individual transcripts also demonstrate distinct patterns of deadenylation in in vitro systems derived from HeLa and Jurkat T cell cytoplasmic extracts. The major patterns observed were slow/synchronous and fast/asynchronous poly(A) tail shortening. For all RNA substrates tested, PARN was shown to be the enzyme responsible for the deadenylation patterns that were observed. Sequences in the 3' untranslated regions influenced the deadenylation pattern. Using a fragment of the 3'UTR of the c-fos mRNA as a model, the interaction of CUG-BP, the human homolog of EDEN-BP - a protein previously implicated in regulated deadenylation in Xenopus oocytes - was shown to be associated with changes in PARN-mediated deadenylation patterns. Our results suggest that association of CUG-BP with 3'UTR sequences can modulate the activity of the PARN deadenylase in mammalian cell extracts.