Transcriptional regulation of meiosis in budding yeast

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Figure legends Fig. 1. Developmental choices of MATa/MATα diploid cells of Saccharomyces cerevisiae. In the presence of carbon and nitrogen sources cells adopt the yeast form morphology; upon nitrogen limitation and in the presence of high levels of glucose, a dimorphic transition to a filamentous growth reminiscent of hyphae takes places. In the absence of nitrogen and glucose and the presence of acetate as the sole carbon source cell enter the meiotic cycle, forming four haploid spores engulfed in a sac, the ascus. Fig. 2. A transcriptional cascade governs initiation of meiosis. The meiotic signals, i.e. the presence of Mata1 and Matα2, the absence of glucose and nitrogen and the presence of acetate leads to G1 arrest as well as to the expression and activity of Ime1. IME1 encodes a transcriptional activator required for the transcription of early meiosis-specific genes (EMG). EMG are involved with premeiotic DNA replication and meiotic recombination. Ndt80 and Ime2, a transcriptional activator and a protein kinase, whose transcription depends on Ime1, are required for the transcription of middle meiosis-specific genes (MMG). MMG are involved with nuclear division and spore formation. The transcription of the late meiosis-specific genes (LMG) depends on Ime1 and Ime2, and these genes are required for spore maturation. The nutrient signal has a direct affect also on the activity of Ime2 and the transcription of LMG. An arrow represents a positive role, a line a negative role. A scissors symbolizes the negative feedback role of Ime2 in regulating degradation of Ime1. Fig. 3. Schematic structure of IME1 5’ untranslated region. The regulated transcription of IME1 is mediated by the combinatorial effect of distinct elements. The MAT signal mediates repression activity of 2 elements UCS3 and UCS4. The carbon source signal is transmitted to four elements. UCS1, UASru and IREu function as repression elements in the presence of glucose. In addition, UASru IREu, as well as UASrm function as activation elements in the absence of glucose and the presence of acetate as the sole carbon source. UCS1 functions as a negative element in the presence of nitrogen. Filled boxs - elements required for transcriptional activation. Open boxs – elements whose function is only to repress transcription. A positive role is marked with an arrow, a negative role by a line. Larger effects are denoted by heavier lines while lesser effects are denoted by slender lines. 59
Fig. 4. The function of positive and negative elements regulating the transcription of IME1. IME1 with various portions of its 5’ untranslated region were fused at the sixth amino acid to the E.coli lacZ gene. The chimeric genes were integrated at the LEU2 loci of a MATa/MATα diploid (strain Y4122, S288C background). Samples were taken from 1x10 7 cells grown in either SD (synthetic glucose) or PSP2 (SA – synthetic acetate (Kassir and Simchen, 1991). In addition, cells grown in PSP2 to 1x10 7 were washed once in water and resuspended in SPM (sporulation media (Kassir and Simchen, 1991). Samples were taken to extract proteins and measure lacZ levels after 3 and 6 h 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%. The studied elements are marked as filled boxes. A nested deletion is marked by a line. NT – not tested. Fig. 5. Cdc25 transmits the nitrogen signal that modulates the repression activity of UCS1, a URS element in IME1 5’ region. UCS1 was inserted between HIS4 UAS and the TATA box in a his4-lacZ chimera. The level of β-Galactosidase was determined in three to five independent transformants. Standard deviations were less than 10%. The results are given as relative levels in comparison (in each case) to the level of expression of UASHIS4-his4-lacZ (control). Insertion of UCS1 in the heterologous UASHIS4-his4-lacZ chimera leads to a substantial reduction in its expression in vegetative growth conditions. Partial relief of repression is observed upon nitrogen depletion, suggesting that the activity of UCS1 as a URS element is mediated by nitrogen. Depletion of Cdc25 by shifting cdc25-5 cells to the non-permissive temperature leads to relief of repression in vegetative growth media, and has no effect upon nitrogen depletion (SPM), suggesting that Cdc25 transmits the nitrogen signal to UCS1. Fig. 6: The UAS activity of the IME1 elements UASru, IREu and UASrm is modulated by the carbon source. His4-lacZ fusions carrying various elements from IME1 5’ untranslated region were integrated at the LEU2 loci of a MATa/MATα diploid (strain Y4122, S288C background). Cells were grown in either SD (synthetic glucose) or PSP2 (SA – synthetic acetate (Kassir and Simchen, 1991). In addition, cells grown in PSP2 to 1x10 7 were washed once in water and resuspended in SPM [sporulation media (Kassir and Simchen, 1991)] and incubated for 6 hours. Samples were taken from 1x10 7 cells/ml to extract proteins and measure lacZ levels. The level of β-Galactosidase is 60
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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
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 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: Yoshida, M., Kawaguchi, H., Sakata,
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
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