Transcriptional regulation of meiosis in budding yeast

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observed upon nitrogen starvation (Xiao and Mitchell, 2000). Single deletion of RIM11, MCK1 or MRK1 has no effect on the in vivo pattern of phosphorylation of Ume6 (Xiao and Mitchell, 2000), but a substantial reduction in the pattern of phosphorylation is observed for the rim11∆ mck1∆ mrk1∆ triple mutant (Xiao and Mitchell, 2000). The redundant function of these GSK3-β homologs is also evident in cells carrying the partially active rim11K68R allele. Efficient sporulation is observed for cells carrying the MCK1 MRK1 wild type alleles, and no sporulation in either mck1∆ MRK1 or MCK1 mrk1∆ strains (Xiao and Mitchell, 2000). Ume6 sequence reveals several consensus sites for phosphorylation by the mammalian GSK3-β homolog. Simultaneous substitution of serine and threonine residues to alanine in one such site (T99A T103A T107) leads to a reduction in phosphorylation, and concomitantly a dramatic reduction in the ability of Ume6(1-232) to interact with Ime1, suggesting that phosphorylation is a prerequisite for interaction (Xiao and Mitchell, 2000). The two-hybrid method demonstrates that the interaction between Rim11 and Ume6 is regulated by the carbon source; the interaction is low in glucose growth media and it is increased in acetate growth media (Malathi et al., 1997). However, coIP shows physical association between Ume6 and Rim11 that is independent on nutrients (Malathi et al., 1997). The authors suggest that this is due to lower levels of Galbd-Ume6 in glucose versus acetate growth media (Malathi et al., 1997). However, it is also possible that this is due to the inability of the Gal4(bd)- Rim11/Gal4(ad)-Ume6 complex to activate transcription, due to the activity of Sin3/Rpd3. Nevertheless, the ability of Rim11 to in vitro phosphorylate Ume6 is increased when both proteins are isolated from acetate grown cells, suggesting that the carbon source regulates either the activity of Rim11, or the ability of its substrate, Ume6, to be phosphorylated (Malathi et al., 1997). The association of Ime1 with Ume6, and the association of Rim11 with both Ime1 and Ume6 suggest that one association may serve as a scaffold for the second association. There are no direct evidence for association of Rim11 with Ime1 and Ume6 in cells deleted for UME6 or IME1, respectively. However, a Gal4ad-Ume6T99N mutant protein shows no interaction with Rim11 in a two-hybrid assay, and reduced interaction with Ime1 (Malathi et al., 1997). These results suggest that either the association between Ume6 and Rim11 is required for the interaction between Ime1 and Ume6 (Malathi et al., 1997), or that the Ume6 T99 residue is required for the association of Ume6 with both Rim11 and Ime1. 3.2. The function of Rim15. Rim15 is absolutely required for the transcription of EMG such as IME2, HOP1 and SPO13 (Vidan and Mitchell, 1997). As described above (section IIIC1.2), Rim15 is required for the transcription of IME1, however, expression of IME1 from an 27
heterologous promoter does not suppress this phenotype, suggesting that Rim15 is required for an additional event. Indeed, Rim15 is required for efficient interaction between Ime1 and Ume6, in cells deleted for RIM15 5-fold reduction in their interaction is observed (Vidan and Mitchell, 1997). This effect is probably due to the effect of Rim15 on Ume6. It is required for complete in vivo phosphorylation of Ume6 in SA and SPM media (Xiao and Mitchell, 2000). Rim15 is not required for the in vitro kinase activity of Rim11 on Ime1 (Vidan and Mitchell, 1997). 4. The function of Gcn5. The conversion of URS1 from a repression to activation element requires the function of the histone acetylase, Gcn5 (Burgess et al., 1999). Diploid cells carrying a recessive mutation in GCN5 arrest under meiotic conditions prior to premeiotic DNA replication and meiotic recombination (Burgess et al., 1999). These cells express IME1, but are defective in the transcription of IME2 (Burgess et al., 1999). Using antibodies directed against acetylated histones H3 and H4, Burges et al., show that under meiotic conditions, depending on Gcn5, specific hyper acetylation on histone H3 is observed in the IME2 promoter (Burgess et al., 1999). Deletion of RPD3 that is required for deacetylation of Histone H4 in the IME2 promote, does not suppress gcn5, suggesting that acetylation of histones is a prerequisite for the transcription of EMG (Burgess et al., 1999). It is not known how Gcn5 is recruited to the promoter of IME2 or additional EMG. 5. The transcription of EMG is also regulated by positive elements. In addition to the negative element, URS1, the promoters of EMG carry positive elements required for their transcription under meiotic conditions: UASH element in HOP1, and the T4C sequence in IME2 (Bowdish and Mitchell, 1993; Vershon et al., 1992). Homologous sequences are found in additional EMG (Chu et al., 1998). Deletion or mutations of these elements prevent high-level expression of EMG (Bowdish and Mitchell, 1993; Vershon et al., 1992). Abf1 binds to the UASH element (Gailus-Durner et al., 1996). ABF1 encodes an essential DNA-binding transcriptional activator required for the transcription of various genes as well as for DNA replication; it binds to origins of DNA replication (Svetlov and Cooper, 1995). The protein that binds the T4C element in IME2 is not known. 6. Additional positive regulators. Ime2, Rim4, and Ndt80 are early and early late genes required for high-level transcription of EMG. Detailed description on their functions is given in section VA. 28
Page 1 and 2: Transcriptional regulation of meios
Page 3 and 4: 3. Proteins required for the associ
Page 5 and 6: I. Introduction The budding yeast S
Page 7 and 8: et al., 2000). On the other hand, i
Page 9 and 10: the UCS4 element upstream of the CY
Page 11 and 12: egulator of Cyr1, CDC25 encodes the
Page 13 and 14: 1998). Furthermore, unlike IREu, IR
Page 15 and 16: In the absence of glucose Sok2 does
Page 17 and 18: autophosphorylation, including on a
Page 19 and 20: hours in SPM, followed by a decline
Page 21 and 22: 4. The SIN3, UME6, and RPD3 genes.
Page 23 and 24: 1993). Nevertheless, when Ime1 is t
Page 25 and 26: However, direct demonstration of ph
Page 27: 3. Proteins required for the associ
Page 31 and 32: expressed only in the absence of gl
Page 33 and 34: structure of hCDK2 reveals that cyc
Page 35 and 36: terminal non-essential domain (Komi
Page 37 and 38: is dependent on Ime2, but in cells
Page 39 and 40: VI. Transcriptional regulation of l
Page 41 and 42: The transcriptional activator that
Page 43 and 44: Functional interaction between Ime1
Page 45 and 46: Bowdish, K. S., and Mitchell, A. P.
Page 47 and 48: Foiani, M., Nadjar-Boger, E., Capon
Page 49 and 50: Jeffrey, P. D., Russo, A. A., Polya
Page 51 and 52: Lindgren, A., Bungard, D., Pierce,
Page 53 and 54: Pazin, M. J., and Kadonaga, J. T. (
Page 55 and 56: Shenhar, G. (2001). TRANSCRIPTIONAL
Page 57 and 58: Szent-Gyorgyi, C. (1995). A biparti
Page 59 and 60: Yoshida, M., Kawaguchi, H., Sakata,
Page 61 and 62: Fig. 4. The function of positive an
Page 63 and 64: Fig. 9. A schematic structure of IM
Page 65 and 66: activation by Ime2 is due to phosph
Page 67 and 68: MCK1 Protein kinase required for ef
Page 69: UME3 A cyclin C homolog that associ

Transcriptional regulation of meiosis in budding yeast

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