Identification of two cis-acting elements that independently regulate the length of poly(A) on Xenopus albumin pre-mRNA
JAYDIP DAS GUPTA a1 , HAIDONG GU a1 , ELENA CHERNOKALSKAYA a1 p1 , XIAOPING GAO a1 p2 and DANIEL R. SCHOENBERG a1 c1
a1 Department of Pharmacology and Comprehensive Cancer Center, The Ohio State University College of Medicine, Columbus, Ohio 43210-1239, USA
Unlike most eukaryotic mRNAs studied to date, Xenopus serum albumin mRNA has a short (17-residue), discrete poly(A) tail. We recently reported that this short poly(A) tail results from regulation of the length of poly(A) on albumin pre-mRNA. The purpose of the present study was to locate the cis-acting element responsible for this, the poly(A)-limiting element or PLE. An albumin minigene consisting of albumin cDNA joined in exon 13 to the 3[prime prime or minute] end of the albumin gene produced mRNA with <20 nt poly(A) when transfected into mouse fibroblasts. This result indicates both that cis-acting sequences that regulate poly(A) length are within this construct, and that nuclear regulation of poly(A) length is conserved between vertebrates. Poly(A) length regulation was retained after replacing the terminal 53 bp and 3[prime prime or minute] flanking region of the albumin gene with a synthetic polyadenylation element (SPA). Conversely, fusing albumin gene sequence spanning the terminal 53 bp of the albumin gene and 3[prime prime or minute] flanking sequence onto the human [beta]-globin gene yielded globin mRNA with a 200-residue poly(A)tail. These data indicate that the PLE resides upstream of the sequence elements involved in albumin pre-mRNA 3[prime prime or minute] processing. Poly(A) length regulation was restored upon fusing a segment bearing albumin intron 14, exon 15, and 3[prime prime or minute] flanking sequence onto the [beta]-globin gene. We demonstrate that exon 15 contains two PLEs that can act independently to regulate the length of poly(A).(Received November 25 1997)
(Revised January 9 1998)
(Accepted April 14 1998)
Key Words: albumin mRNA; mRNA 3[prime prime or minute]; processing; polyadenylation; poly(A) length regulation.
c1 Reprint requests to: Daniel Schoenberg, Department of Pharmacology, The Ohio State University College of Medicine, 333 West 10th Avenue, Columbus, Ohio 43210-1239, USA; e-mail: firstname.lastname@example.org.
p1 Present address: ESA, Inc., 22 Alpha Road, Chelmsford, Massachusetts 01824, USA.
p2 Present address: Genpower Inc., 6106 Hana Road, Edison, New Jersey, New Jersey 08817, USA.