Precursor-product discrimination by La protein during tRNA metabolism.
La proteins bind pre-tRNAs at their UUU-3'OH ends, facilitating their maturation. Although the mechanism by which La binds pre-tRNA 3' trailers is known, the function of the RNA binding beta-sheet surface of the RNA-recognition motif (RRM1) is unknown. How La dissociates from UUU-3'OH-containing trailers after 3' processing is also unknown. Here we show that La preferentially binds pre-tRNAs over processed tRNAs or 3' trailer products through coupled use of two sites: one on the La motif and another on the RRM1 beta-surface that binds elsewhere on tRNA. Two sites provide stable pre-tRNA binding, whereas the processed tRNA and 3' trailer are released from their single sites relatively fast. RRM1 loop-3 mutations decrease affinity for pre-tRNA and tRNA, but not for the UUU-3'OH trailer, and impair tRNA maturation in vivo. We propose that RRM1 functions in activities that are more complex than UUU-3'OH binding. Accordingly, the RRM1 mutations also impair an RNA chaperone activity of La. The results suggest how La distinguishes precursor from product RNAs, allowing it to recycle onto a new pre-tRNA.
Bayfield
Mark A
MA
Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA.
Maraia
Richard J
RJ
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001324:Autoantigens / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012322:RNA Precursors / Q000378:metabolism*; D012343:RNA, Transfer / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000737:chemistry / Q000378:metabolism*; D000097585:SS-B Antigen
D001324:Autoantigens; D012322:RNA Precursors; D012343:RNA, Transfer; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D000097585:SS-B Antigen