Transcriptional regulation of meiosis in budding yeast

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given in Miller units. The results are the averages of three to five independent transformants. Standard deviations were less than 10%. UASru, IREu and UASrm support the expression of his4-lacZ, suggesting that all three elements possess a UAS activity. The UAS activity is low in SD, and increased activity is observed in SA and SPM media, suggesting that their activity is repressed by glucose and/or depends on acetate. The IREd element that is homologus to IREu (see Fig. 8) shows very low UAS activity. Fig. 7. cAMP reduces sporulation and the expression of IME1 through the IREu element. MATa/MATα diploid cells (strain Y4122, S288C background) carrying ime1-lacZ or his4-lacZ fusions with various elements from IME1 5’ untranslated region integrated at the LEU2 loci. Cells were grown in PSP2 [synthetic acetate (Kassir and Simchen, 1991)] with or without 10mM cAMP to 1x10 7 cells/ml, washed once in water and resuspended in SPM [sporulation media (Kassir and Simchen, 1991)] with or without 10mM cAMP, respectively. Samples were taken at 6 hours in SPM. The level of β-Galactosidase is given in Miller units. The results are the averages of three to five independent transformants. Standard deviations were less than 10%. At 24 hours in SPM samples were taken to count the percentage of asci. Results are given as relative levels. Addition of cAMP leads to a reduction in sporulation (72.6% and 49.8% in the absence and presence of cAMP, respectively) as well as a reduction in the expression of ime1-lacZ. We assume that the minor effect is due to the function of the cAMP specific phosphodiesterases. Addition of cAMP reduces the UAS activity of IREu while it has no effect on the activity of either UASru or UASrm. Fig. 8. IREu and IREd are almost identical repeats in IME1 5’ region carrying the known UAS sequences STRE and SCB. Sequence alignments of IREu (upstream) and IREd (downstream) to the stress response element (STRE) and the Swi4/6 Cycle box (SCB). We suggest that Msn2 binds the STRE element in IREu since Msn2 binds IREu as well as STRE elements in stress response genes. We further suggest that Sok2 binds the SCB element since it is highly homologous to the DNA-binding domain of Swi4 that binds such elements, and since genetic analysis reveals that it binds IREu (see text). The physical association between Sok2 and Msn2 suggests that they bind the DNA as a heterodimer. 61
Fig. 9. A schematic structure of IME1 5’ untranslated region showing the positive and negative transcription factors which regulate its expression. The regulated transcription of IME1 is mediated by the combinatorial effect of distinct elements. The MAT signal is transmitted to UCS4 by Rme1. The activity of Rme1 as a repressor requires Rgr1 and Sin4. The cAMP/PKA signal transduction pathway transmits the glucose signal to IREu through two transcription factors, Sok2 and Msn2. In glucose growth media phosphorylation of Sok2 by PKA promotes its repression activity, whereas phosphorylation of Msn2 sequesters the protein in the cytoplasm. In acetate growth media Sok2 repression is relieved by a decrease in the activity of PKA, as well as by the function of Ime1. The increased binding of Msn2 to IREu leads to transcriptional activation. Yhp1 binds to UASv, however, its activity is not required for the transcription of IME1. Nitrogen, via Cdc25, regulates the URS activity of UCS1. It is not known whether the effect of Cdc25 is mediated through the cAMP/PKA and/or MAPK pathways. Filled box - elements required for transcriptional activation. Open box – elements that whose function is only to repress transcription. A positive role is marked with an arrow, a negative role in line. Dashed lines and a question mark – preliminary data. Fig. 10. The expression and activity of Ime1 are regulated by nutrients. Schematic representation on how glucose and nitrogen regulates the availability and activity of Ime1. The nucleus is depicted between the two circular lines, and cell membrane by a heavy line. A positive role is marked with an arrow, a negative role by a straight line. The transcription of IME1 is inhibited in the presence of glucose and nitrogen. Translation of IME1 mRNA is inhibited in the presence of a nitrogen source. In the presence of nitrogen, Ime1is sequestered from the nuclei due to phosphorylation by Cdc28/Cln. Interaction of Ime1 with Ume6, and consequently transcriptional activation of early meiosis-specific genes (EMG) is inhibited by glucose and nitrogen. Fig. 11. Conditions leading to the choice between silencing and expression of early meiosisspecific genes. A. Vegetative growth conditions B. Meiotic conditions. Ume6 binds to the URS1 element in early-meiosis specific genes (EMG) under all growth conditions. In vegetative growth conditions Ume6 recruits to repression complexes, Sin3/Rpd3 and Isw2, leading to histone H4 deacetylase and chromatin remodeling, respectively, and silencing. Under these conditions Rim15 and most probably Rim11 are non-active. The activity of Rim15 is repressed by PKA (Tpk1,2,3) phosphorylation. Under meiotic conditions (acetate 62
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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
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 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: Fig. 4. The function of positive an
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
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