Unique properties of the Mtr4p-poly(A) complex suggest a role in substrate targeting.
Mtr4p is a DEVH-box helicase required for 3'-end processing and degradation of various nuclear RNA substrates. In particular, Mtr4p is essential for the creation of 5.8S rRNA, U4 snRNA, and some snoRNAs and for the degradation of cryptic unstable transcripts (CUTs), aberrant mRNAs, and aberrant tRNAs. Many instances of 3'-end processing require limited polyadenylation to proceed. While polyadenylation can signal degradation in species from bacteria to humans, the mechanism whereby polyadenylated substrates are delivered to the degradation machinery is unknown. Our previous work has shown that Mtr4p preferentially binds poly(A) RNA. We suspect that this preference aids in targeting polyadenylated RNAs to the exosome. In these studies, we have investigated the mechanism underlying the preference of Mtr4p for poly(A) substrates as a means of understanding how Mtr4p might facilitate targeting. Our analysis has revealed that recognition of poly(A) substrates involves sequence-specific changes in the architecture of Mtr4p-RNA complexes. Furthermore, these differences significantly affect downstream activities. In particular, homopolymeric stretches like poly(A) ineffectively stimulate the ATPase activity of Mtr4p and suppress the rate of dissociation of the Mtr4p-RNA complex. These findings indicate that the Mtr4p-poly(A) complex is unique and ideally suited for targeting key substrates to the exosome.
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201, United States.
Jade
J
Bernstein
Jeff D
JD
Ballin
Dimeka N
DN
Patterson
Gerald M
GM
Wilson
Eric A
EA
Toth
D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005454:Fluorescence Polarization; D018390:Gene Targeting / Q000379:methods; D026723:Polyadenylation / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017423:Sequence Analysis, RNA; D013379:Substrate Specificity / Q000235:genetics
D012331:RNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D000255:Adenosine Triphosphate; C101004:MTR4 protein, S cerevisiae; D053487:DEAD-box RNA Helicases