MCB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Lo, H.-J.
Right arrow Articles by Donahue, T. F.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Lo, H.-J.
Right arrow Articles by Donahue, T. F.

Next Article 

Mol Cell Biol, February 1998, p. 665-675, Vol. 18, No. 2
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

RNA Polymerase I-Promoted HIS4 Expression Yields Uncapped, Polyadenylated mRNA That Is Unstable and Inefficiently Translated in Saccharomyces cerevisiae

Hsiu-Jung Lo,dagger Han-Kuei Huang, and Thomas F. Donahue*

Department of Biology, Indiana University, Bloomington, Indiana 47405

Received 28 March 1997/Returned for modification 8 May 1997/Accepted 6 November 1997

The HIS4 gene in Saccharomyces cerevisiae was put under the transcriptional control of RNA polymerase I to determine the in vivo consequences on mRNA processing and gene expression. This gene, referred to as rhis4, was substituted for the normal HIS4 gene on chromosome III. The rhis4 gene transcribes two mRNAs, of which each initiates at the polymerase (pol) I transcription initiation site. One transcript, rhis4s, is similar in size to the wild-type HIS4 mRNA. Its 3' end maps to the HIS4 3' noncoding region, and it is polyadenylated. The second transcript, rhis4l, is bicistronic. It encodes the HIS4 coding region and a second open reading frame, YCL184, that is located downstream of the HIS4 gene and is predicted to be transcribed in the same direction as HIS4 on chromosome III. The 3' end of rhis4l maps to the predicted 3' end of the YCL184 gene and is also polyadenylated. Based on in vivo labeling experiments, the rhis4 gene appears to be more actively transcribed than the wild-type HIS4 gene despite the near equivalence of the steady-state levels of mRNAs produced from each gene. This finding indicated that rhis4 mRNAs are rapidly degraded, presumably due to the lack of a cap structure at the 5' end of the mRNA. Consistent with this interpretation, a mutant form of XRN1, which encodes a 5'-3' exonuclease, was identified as an extragenic suppressor that increases the half-life of rhis4 mRNA, leading to a 10-fold increase in steady-state mRNA levels compared to the wild-type HIS4 mRNA level. This increase is dependent on pol I transcription. Immunoprecipitation by anticap antiserum suggests that the majority of rhis4 mRNA produced is capless. In addition, we quantitated the level of His4 protein in a rhis4 xrn1Delta genetic background. This analysis indicates that capless mRNA is translated at less than 10% of the level of translation of capped HIS4 mRNA. Our data indicate that polyadenylation of mRNA in yeast occurs despite HIS4 being transcribed by RNA polymerase I, and the 5' cap confers stability to mRNA and affords the ability of mRNA to be translated efficiently in vivo.

* Corresponding author. Mailing address: Department of Biology, Indiana University, Jordan Hall A305, Bloomington, IN 47405. Phone: (812) 855-8883. Fax: (812) 855-6705. E-mail: donahue{at}bio.indiana.edu.

dagger Present address: Whitehead Institute for Biomedical Research Cambridge, MA 02142-1479.




This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. J. Virol. Eukaryot. Cell
Microbiol. Mol. Biol. Rev. Clin. Vaccine Immunol. All ASM Journals

Copyright © 1998 by the American Society for Microbiology. All rights reserved.