MULTIPLE REGIONS OF YEAST RIBOSOMAL-PROTEIN L1 ARE IMPORTANT FOR ITS INTERACTION WITH 5-S RIBOSOMAL-RNA AND ASSEMBLY INTO RIBOSOMES

Yeast ribosomal protein L1 binds to 5 S rRNA and can be released from 60 S ribosomal subunits as an intact ribonucleoprotein particle. To id entify residues important for binding of Saccharomyces cerevisiae rpL1 to 5 S rRNA and assembly into functional ribosomes, we have isolated mutant alleles of the yeast RPL1 gene by site-directed and random muta genesis. The rpl1 mutants were assayed for association of rpL1 with 5 S rRNA in vivo and in vitro and assembly of rpL1 into functional 60 S ribosomal subunits. Consistent with previous data implicating the impo rtance of the carboxyl-terminal 47 amino acids of rpL1 for binding to 5 S rRNA in vitro, we find that deletion of the carboxyl-terminal 8, 2 5, or 44 amino acids of rpL1 confers lethality in vivo. Missense mutat ions elsewhere in rpL1 also affect its function, indicating that multi ple regions of rpL1 are important for its association with 5 S rRNA an d assembly into ribosomes.