Transcriptional regulation of meiosis in budding yeast

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media and nitrogen depletion) phosphorylation of Ime1and Ume6 by Rim11 and Rim15 promotes the interaction of Ime1 with Ume6. Ime1 function is required to relieve repression by Sin3 and to activate transcription. In addition, transcriptional activation depends on histone acetylation by Gcn5. Fig. 12. Ime2 is highly homologous to hCDK2. A. Sequence alignment of Ime2 to hCDK2. B, Ribbon depiction of the crystal structure of hCDK2 (Protein Data Bank structure code 1HCL). C. Ribbon depiction of the homology based model of Ime2 based on the CDK structure. The following stretches of residues are colored for clarity: the ATP binding site (yellow), The PSTAIRE site (orange), the Catalytic site (red) and the T-loop (blue). The Ime2 model was prepared using the 3D-PSSM modeling algorithm (Kelley et al., 2000). The figures were prepared using InsightII (Accelrys). Fig. 13. Transcriptional regulation of middle meiosis-specific genes. Ndt80 is the transcriptional activator binding to the MSE element present in the 5’ region of all middle meiosis-specific genes (MMG). A subset of MMG carries an MSE* site (SMK1 in comparison to CLB1) that can be bound by Sum1. Sum1 associates with Hst1 that functions as histone deacetylase, thus leading to silencing under vegetative growth conditions and at early meiotic times. Under meiotic conditions relief of repression is due to degradation of Sum1 by Ime2. Sum1 also represses the transcription of NDT80, since it carries both an MSE and MSE* elements. In addition, NDT80 carries two URS1 elements that are bound by Ume6. In vegetative growth media Ume6 recruits the Sin3/Rpd3 histone deacetylase complex that represses transcription. Under meiotic conditions Ume6 recruits Ime1 that can activate transcription, but only in the absence of Sum1. Ime2 phosphorylates Ndt80, and this phosphorylation may contribute to the complete transcriptional activity of Ndt80. In the absence of meiotic recombination the pachytene checkpoint inhibits degradation of Sum1 and phosphorylation of Ndt80. Consequently, the level of Ndt80 is reduced, and the unphosphorylated Ndt80 is impaired in activating the transcription of MMG. Fig. 14. Positive and negative feedback loops control meiosis. Ime1 shows positive autoregulation that is required to relieve repression mediated by Sok2 and thus for its high-level transcription. Expression of early meiosis-specific genes (EMG) requires relief of repression of Sin3 and transcriptional activation, two functions that are promoted by Ime1. The transcription of middle genes (MMG) depends on Ime2 and Ndt80. Transcriptional 63
activation by Ime2 is due to phosphorylation of the transcriptional activator, Ndt80, and degradation of the transcriptional repressor, Sum1. Ime2 exhibits a negative feedback role, it is required to shut down the transcription of IME1. Since Ime2 directly phosphorylates Ime1, and since this phosphorylation is required for degradation of Ime1 by the 26S proteasome, it was suggested that the reduction in the transcription of IME1 as well as EMG is due to the absence of Ime1 and reestablishment of repression by Sok2 and Sin3, respectively. The transcription of MMG is repressed by the pachytene checkpoint that inhibits phosphorylation of Ndt80 and degradation of Sum1. 64
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Transcriptional regulation of meios
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3. Proteins required for the associ
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I. Introduction The budding yeast S
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et al., 2000). On the other hand, i
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the UCS4 element upstream of the CY
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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 and 28: 3. Proteins required for the associ
Page 29 and 30: heterologous promoter does not supp
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: Fig. 9. A schematic structure of IM
Page 67 and 68: MCK1 Protein kinase required for ef
Page 69: UME3 A cyclin C homolog that associ
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