RNA-protein interactions promote asymmetric sorting of the ASH1 mRNA ribonucleoprotein complex.
In Saccharomyces cerevisiae, ASH1 mRNA is localized to the tip of daughter cells during anaphase of the cell cycle. ASH1 mRNA localization is dependent on four cis-acting localization elements as well as Myo4p, She2p, and She3p. Myo4p, She2p, and She3p are hypothesized to form a heterotrimeric protein complex that directly transports ASH1 mRNA to daughter cells. She2p is an RNA-binding protein that directly interacts with ASH1 cis-acting localization elements and associates with She3p. Here we report the identification of seven She2p mutants-N36S, R43A, R44A, R52A, R52K, R63A, and R63K-that result in the delocalization of ASH1 mRNA. These mutants are defective for RNA-binding activity but retain the ability to interact with She3p, indicating that a functional She2p RNA-binding domain is not a prerequisite for association with She3p. Furthermore, the nuclear/cytoplasmic distribution for the N36S and R63K She2p mutants is not altered, indicating that nuclear/cytoplasmic trafficking of She2p is independent of RNA-binding activity. Using the N36S and R63K She2p mutants, we observed that in the absence of She2p RNA-binding activity, neither Myo4p nor She3p is asymmetrically sorted to daughter cells. However, in the absence of She2p, Myo4p and She3p can be asymmetrically segregated to daughter cells by artificially tethering mRNA to She3p, implying that the transport and/or anchoring of the Myo4p/She3p complex is dependent on the presence of associated mRNA.
Gonsalvez
Graydon B
GB
Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
Lehmann
Katrina A
KA
Ho
Derek K
DK
Stanitsa
Eleni S
ES
Williamson
James R
JR
Long
Roy M
RM
D004268:DNA-Binding Proteins / Q000235:genetics*; D017354:Point Mutation; D011233:Precipitin Tests; D011485:Protein Binding; D012331:RNA, Fungal / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012261:Ribonucleoproteins / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*; D020798:Two-Hybrid System Techniques
C098733:ASH1 protein, S cerevisiae; D004268:DNA-Binding Proteins; C477782:IST2 protein, S cerevisiae; D012331:RNA, Fungal; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D012261:Ribonucleoproteins; C471175:SHE2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors