Lsm proteins bind and stabilize RNAs containing 5' poly(A) tracts.
Many orthopoxvirus messenger RNAs have an unusual nontemplated poly(A) tract of 5 to 40 residues at the 5' end. The precise function of this feature is unknown. Here we show that 5' poly(A) tracts are able to repress RNA decay by inhibiting 3'-to-5' exonucleases as well as decapping of RNA substrates. UV cross-linking analysis demonstrated that the Lsm complex associates with the 5' poly(A) tract. Furthermore, recombinant Lsm1-7 complex specifically binds 5' poly(A) tracts 10 to 21 nucleotides in length, consistent with the length of 5' poly(A) required for stabilization. Knockdown of Lsm1 abrogates RNA stabilization by the 5' poly(A) tract. We propose that the Lsm complex simultaneously binds the 3' and 5' ends of these unusual messenger RNAs and thereby prevents 3'-to-5' decay. The implications of this phenomenon for cellular mRNA decay are discussed.
Bergman
Naomi
N
Department of Microbiology, Immunology & Pathology, Colorado State University, Fort Collins, Colorado 80525, USA.
Moraes
Karen C M
KC
Anderson
John R
JR
Zaric
Bozidarka
B
Kambach
Christian
C
Schneider
Robert J
RJ
Wilusz
Carol J
CJ
Wilusz
Jeffrey
J
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D006224:Cricetinae; D017931:DNA Primers; D008565:Membrane Proteins / Q000378:metabolism*; D011061:Poly A / Q000378:metabolism*; D011485:Protein Binding; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014466:Ultraviolet Rays
D017931:DNA Primers; D008565:Membrane Proteins; D011994:Recombinant Proteins; D011061:Poly A; D012313:RNA