Previous Article | Next Article ![]()
Molecular and Cellular Biology, April 1999, p. 2672-2680, Vol. 19, No. 4
Department of Molecular Microbiology and
Biotechnology, Faculty of Life Sciences, Tel-Aviv University,
Tel-Aviv 69978, Israel
Received 2 September 1998/Returned for modification 30 October
1998/Accepted 5 January 1999
Rpb4 and Rpb7 are two yeast RNA polymerase II (Pol II) subunits
whose mechanistic roles have recently started to be deciphered. Although previous data suggest that Rpb7 can stably interact with Pol
II only as a heterodimer with Rpb4, RPB7 is essential for viability, whereas RPB4 is essential only during some
stress conditions. To resolve this discrepancy and to gain a better
understanding of the mode of action of Rpb4, we took advantage of the
inability of cells lacking RPB4 (rpb4
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Rpb7 Can Interact with RNA Polymerase II and Support
Transcription during Some Stresses Independently of Rpb4
,
containing Pol II
4) to grow above 30°C and screened for genes
whose overexpression could suppress this defect. We thus discovered
that overexpression of RPB7 could suppress the inability of
rpb4
cells to grow at 34°C (a relatively mild
temperature stress) but not at higher temperatures. Overexpression of
RPB7 could also partially suppress the cold sensitivity of rpb4
strains and fully suppress their inability to
survive a long starvation period (stationary phase). Notably, however,
overexpression of RPB4 could not override the requirement
for RPB7. Consistent with the growth phenotype,
overexpression of RPB7 could suppress the transcriptional
defect characteristic of rpb4
cells during the mild, but
not during a more severe, heat shock. We also demonstrated, through two
reciprocal coimmunoprecipitation experiments, a stable interaction of
the overproduced Rpb7 with Pol II
4. Nevertheless, fewer Rpb7
molecules interacted with Pol II
4 than with wild-type Pol II. Thus,
a major role of Rpb4 is to augment the interaction of Rpb7 with Pol II.
We suggest that Pol II
4 contains a small amount of Rpb7 that is
sufficient to support transcription only under nonstress conditions.
When RPB7 is overexpressed, more Rpb7 assembles with Pol
II
4, enough to permit appropriate transcription also under some
stress conditions.
*
Corresponding author. Mailing address: Department of
Molecular Microbiology and Biotechnology, Faculty of Life Sciences,
Tel-Aviv University, Tel-Aviv 69978, Israel. Phone: (972) 36409030. Fax: (972) 36409407. E-mail:
lcchoder{at}ccsg.tau.ac.il.
This article has been cited by other articles:
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|