Transcriptional regulation of meiosis in budding yeast

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4, lines F,G,H), confirming their function as UAS elements (Sagee et al., 1998; Shenhar and Kassir, 2001). In addition, in the presence of glucose UASru and IREu function as repression elements [Fig. 4, lines F,G and (Shenhar and Kassir, 2001)]. Deletion of UASru increases expression in SD, but in SA or SPM expression is absent (Fig. 4, line F), suggesting that UASru functions as a URS element in the presence of glucose and as a UAS element in the absence of glucose and/or the presence of acetate. Nested deletion of IREu leads to the same levels of expression of ime1-lacZ in both SD and SA media [Fig. 4, line G, (Sagee et al., 1998)], suggesting that its URS activity is regulated by either the carbon or nitrogen source. These UASru, IREu and UASrm element function as a carbon source regulated UAS when inserted upstream of a his4-lacZ reporter gene (Fig. 6). Decreased levels of expression are observed in SD, and increased expression is observed in SA, while in SPM there is a slight increase in activity, but only in the presence of UASru [Fig. 6 and (Sagee et al., 1998)]. These results imply that IREu and UASrm are regulated only by the glucose signal, and that UASru is mainly regulated by glucose but nitrogen has also a partial effect on its activity. 1. The cAMP/PKA signal-transduction pathway. Genetic analysis suggests that the cAMP/PKA signal pathway transmits a nitrogen signal [see section IIIB and (Gancedo, 2001; Pan et al., 2000)]. However, biochemical and genetic analysis demonstrate that this pathway is one of the major signal transduction pathways transmitting a glucose signal to yeast cells. This is an essential pathway that transiently increases the level of cAMP in response to glucose addition [for reviews see (Broach, 1991; Thevelein and de Winde, 1999)]. Addition of 10mM cAMP to diploid cells incubated in sporulation conditions leads to a small but significant reduction in the expression of IME1 and the level of sporulation (Fig. 7). The expression of either UASrm-his4lacZ or UASru-his4-lacZ is slightly increased by addition of cAMP. However, about 1.6-fold reduction in the expression of IREu-his4-lacZ is observed, similar to the effect cAMP has on sporulation and IME1 expression, suggesting that the activity of IREu is negatively regulated by cAMP. The signal transduction pathways that transmit the glucose signal to UASru and UASrm are not known. 1.1. The IREu element. The sequence of IREu (-1153 to –1121) reveals that it includes two known positive elements, a stress response element, STRE, and the Swi4/Swi6 cell cycle box, SCB (Fig. 8). An almost identical element, IREd, is present at –788 to –756 of IME1 (Fig. 3). IREd differs from IREu in two residues localized to the STRE and SCB elements (Fig. 8). An ime1-lacZ chimeras whose 5’ end are terminated downstream or upstream of either IREu or IREd show that IREu functions as a positive element, whereas IREd as a negative element (Sagee et al., 11
1998). Furthermore, unlike IREu, IREd promotes only low UAS activity when inserted upstream of his4-lacZ (Fig. 6), suggesting that the STRE and/or the SCB elements are the transcriptional activation sequences within IREu. The cAMP/PKA pathway negatively regulates IREu, promoting its URS activity and preventing its UAS activity in the presence of glucose (Sagee et al., 1998; Shenhar and Kassir, 2001). Deletion of BCY1- the regulatory subunit of PKA (Toda et al., 1987a) leads to no expression of IREu-his4-lacZ, whereas a temperature sensitive mutations in CDC25 leads to a substantial increase in the activity of IREu in the presence of either glucose or acetate as the sole carbon source (Sagee et al., 1998). Transcription factors that regulate the activity of IREu are the two-homologous DNA-binding proteins, Msn2 and Msn4, Ime1 and Sok2. Msn2 and Msn4 are absolutely required for the activity of IREu, Ime1 is required for the complete UAS activity of IREu, and Sok2 is a negative regulator for IREu activity (Sagee et al., 1998; Shenhar and Kassir, 2001). 1.1.1. Msn2 and Msn4. These C2H2 Zinc-finger proteins bind the STRE site present in many stress-induced genes (Martinez-Pastor et al., 1996; Schmitt and McEntee, 1996), including the IREu and IREd elements in IME1 (Sagee et al., 1998). Competition experiments reveal that IREu is a better competitor than IREd (Sagee et al., 1998), suggesting that Msn2 and Msn4 bind to the STRE element in IREu. In vitro transcribed and translated Msn2 can bind the STRE sequence and the IREu element (Martinez-Pastor et al., 1996; Shenhar, 2001), suggesting that binding is independent of post-translational modifications, and/or the presence of additional proteins. However, two lines of evidence suggest that Msn2 forms a heterodimer with Sok2 (see section IIIC1.1.2 below): i. Msn2 physically associates with Sok2, and ii. Deletion of the postulated Sok2 binding site within IREu (the SCB element) abolishes the activity of IREu (Shenhar and Kassir, 2001). These results suggest that in vivo, Msn2 forms a heterodimer with Sok2, and that Sok2 facilitates its binding to the DNA. In the absence of Sok2, an imposter protein can promote the binding of Msn2/4 to STRE (Fig. 8) (Shenhar and Kassir, 2001). Msn2/4 are apparent targets of the cAMP/PKA pathway. This is concluded from the following observations: i. Deletion of both MSN2 and MSN4 suppresses the lethality of a strain deleted for the three TPK genes [TPK1-3 are the three homologous genes encoding the catalytic activity of PKA (Smith et al., 1998; Toda et al., 1987b)], ii. Msn2 includes sites required for its nuclear import (NLS) as well as for its export (NIS), whose functions are regulated by glucose through the cAMP/PKA pathway (Gorner et al., 2002). Glucose starvation and inactivation of the cAMP/PKA pathway through mutations, leads to nuclear localization, whereas addition of glucose or cAMP leads to cytoplasmic localization (Gorner et al., 1998; Gorner et al., 2002). Interestingly, the NIS element is also regulated by the TOR signaling pathway. When this signal 12
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: egulator of Cyr1, CDC25 encodes the
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 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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