Separate RNA-binding surfaces on the multifunctional La protein mediate distinguishable activities in tRNA maturation.
By sequence-specific binding to 3' UUU-OH, the La protein shields precursor (pre)-RNAs from 3' end digestion and is required to protect defective pre-transfer RNAs from decay. Although La is comprised of a La motif and an RNA-recognition motif (RRM), a recent structure indicates that the RRM beta-sheet surface is not involved in UUU-OH recognition, raising questions as to its function. Progressively defective suppressor tRNAs in Schizosaccharomyces pombe reveal differential sensitivities to La and Rrp6p, a 3' exonuclease component of pre-tRNA decay. 3' end protection is compromised by mutations to the La motif but not the RRM surface. The most defective pre-tRNAs require a second activity of La, in addition to 3' protection, that requires an intact RRM surface. The two activities of La in tRNA maturation map to its two conserved RNA-binding surfaces and suggest a modular model that has implications for its other ligands.
Huang
Ying
Y
Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, US National Institutes of Health, 31 Center Dr., Rm. 2A25, Bethesda, Maryland 20892, USA.
Bayfield
Mark A
MA
Intine
Robert V
RV
Maraia
Richard J
RJ
D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics; D012331:RNA, Fungal / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013489:Suppression, Genetic
D012331:RNA, Fungal; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D029702:Schizosaccharomyces pombe Proteins; C513614:sla1 protein, S pombe; D012343:RNA, Transfer