Mpp10p, a new protein component of the U3 snoRNP required for processing of 18S rRNA precursors.
December 10, 1997
Baserga SJ, Agentis TM, Wormsley S, Dunbar DA, Lee S.Nucleic Acids Symp Ser. 1997;(36):64-7.
We have used the yeast, Saccharomyces cerevisiae, as a model system to identify a new protein component of the U3 small nucleolar ribonucleoprotein (snoRNP) and to study its role in pre-rRNA processing. Mpp10p, which we have cloned and characterized from humans, mice and yeast, is a 110 kDa protein in yeast. Antibodies to it immunoprecipitate the U3 snoRNA, indicating that it is a U3 snoRNP component. MPP10 is an essential gene. Depletion of Mpp10p by repression of MPP10 expressed from a conditional promoter causes slow growth. Analysis of pre-rRNA processing in the depleted cells indicates that Mpp10p is required for processing at the 3 U3 snoRNA-dependent sites in the pre-rRNA (A0, A1, A2). Truncations of terminal charged domains create Mpp10 proteins that confer slow growth at 30 degrees C and/or at 22 degrees C. Analysis of pre-rRNA processing in these mutants indicates a deficiency in processing at only two of the U3 snoRNA-dependent sites in the pre-rRNA (A1 and A2). Therefore truncated Mpp10 proteins are able to separate the function of the U3 snoRNP into a requirement for it in distinct processing events.