Introduction Schizosaccharomyces pombe Saccharomyces cerevisiae S. pombe S. cerevisiae 1994 S. pombe 1990 S. pombe 2004 2004 S. cerevisiae 2005 2003 1991 2001 S. pombe 2003 2005 S. cerevisiae 2004 S. cerevisiae 2001 2003 2005 S. pombe 2002 S. pombe S. cerevisiae 1999 2004 S. pombe S. cerevisiae S. pombe S. cerevisiae S. pombe S. cerevisiae 1999 S. pombe rpb4 rpb4 Materials and methods Strains and molecular genetic methods S. pombe 1 rpb4 nmt1 nmt1 nmt1 1993 1998 2002 1989 S. pombe 1991 Table 1 Strains used in this study Strain Relevant genotype Source JB22 h − 1970 JB394  p3nmt1-rpb4 h − This study JB395 p41nmt1-rpb4 h − This study JB396 p81nmt1-rpb4 h − This study Growth experiments 600  rpb4 nmt1 nmt1 sep1 Quantitative RT-PCR experiments rpb4 rpb4 ® ® rpb4 fba1 Stress response assays Serial dilutions (1/10) of rpb4 strains generated in our study were spotted on EMM plates with or without 15 μM thiamine. The plates were supplemented with 0.5 mM hydrogen peroxide or different concentrations of sorbitol (1, 2, 3 and 4 M) to test the response to oxidative and osmotic stress, respectively. These plates were incubated at 32°C for 2 days and photographed. The effect of temperature stress was tested by incubating the strains at 36°C for 2 days. Microscopy Unfixed cells were observed at 2-h intervals for 25 h by light microscopy using a Zeiss Axioscope fluorescence microscope set up for differential interference contrast (DIC) with a 40× objective and Axiovision digital imaging system. To stain the nuclei, cells were spread onto microscopic glass slides. Subsequently, the cells were fixed by heating at 70°C for 1 min and DAPI (4′,6′ diamidino-2-phenylindole) was added at a final concentration of 1 μg/ml. To view the division septa, calcofluor was added to cultures at a final concentration of 5 mg/ml and the cultures were incubated in the dark at room temperature for 5 min. The cells were washed twice with phosphate buffer saline, and 5 μl of cell suspension was spotted onto microscopic glass slides. DAPI- and calcofluor-treated cells were visualized under a Zeiss Axioscope microscope as above. Microarray experiments rpb4 600  rpb4 2005 2003 http://www.sanger.ac.uk/PostGenomics/S_pombe 2003 Bacillus subtilis 2005 S. pombe www.genedb.org/genedb/pombe/index.jsp http://www.sanger.ac.uk/PostGenomics/S_pombe Results Dosage-dependent effect of Rpb4 on cell growth S. pombe rpb4 nmt1 nmt1 nmt1 nmt1 1993 rpb4 nmt1 nmt1 rpb4 1 rpb4 rpb4 nmt1 nmt1 fba1 rpb4 rpb4 1 rpb4 Fig. 1 rpb4 rpb4 nmt1 nmt1 nmt1 gray bars white bars rpb4 left fba1 right  rpb4 2 rpb4 nmt1 rpb4 nmt1 rpb4 nmt1 nmt1 2 Fig. 2 filled circle rpb4 nmt1 filled square nmt1 filled triangle nmt1 crosses 600 a  b rpb4 nmt1  Effect of Rpb4 on cell growth under stress conditions S. cerevisiae 2004 S. pombe rpb4 rpb4 rpb4 nmt1 3 Fig. 3 rpb4 nmt1 nmt1 a b rpb4 nmt1 rpb4 nmt1 c rpb4 nmt1 d rpb4 nmt1 sep1 ace2 sep1 ace2  rpb4 nmt1 3 3 rpb4 nmt1 rpb4 nmt1 3 3 3 Discussion 3 2005 rpb4 S. pombe Materials and methods 4 Fig. 4 rpb4 a rpb4 nmt1 rpb4 upper right rbp4 b  rpb4 sep10 sep15 2005 P −30 c rbp4 Horizontal rows Columns bottom right gray mcs6, pmh1, sep10 sep15 2005 sep1 ace2 2004  2003 2002 P  −13 −36 2003 2004 2005 2000 P −16 −47 2005 Discussion 4 P −14 2004 4 4 Discussion S. pombe S. pombe 1999 S. cerevisiae 1999 S. cerevisiae 2000 S. pombe S. cerevisiae rpb4 1 2 S. cerevisiae RPB4 1989 2004 S. pombe rpb4 1999 rpb4 rpb4 S. pombe S. cerevisiae 1999 S. pombe 1989 rpb4 3 sec6, sec8, sec10 exo70 mid2 spn3 spn4 agn1 eng1 ppb1 pmk1, pmp1 sep1 ace2 sep10 sep11 sep15 1993 1994 1996 1996 1998 1999 2002 2003 2003 2003 2004 S. cerevisiae rpb4 rpb4 . 2003 rpb4 4 rpb4 eng1 agn1 adg1 adg3 2004 2005 rpb4 sep1 ace2 sep10 sep15 mcs6 pmh1 2001 2003 2005 rpb4 rpb4 4 rpb4 2005 rpb4 rbp4 rpb7 2005 rpb4 S. pombe rpb4 1893 S. pombe 2003 rpb4 Electronic supplementary material Supplementary material