The BUD4 protein of yeast, required for axial budding, is localized to the mother/BUD neck in a cell cycle-dependent manner.

Abstract

A and alpha cells of the yeast Saccharomyces cerevisiae exhibit an axial budding pattern, whereas a/alpha diploid cells exhibit a bipolar pattern. Mutations in BUD3, BUD4, and AXL1 cause a and alpha cells to exhibit the bipolar pattern, indicating that these genes are necessary to specify the axial budding pattern (Chant, J., and I. Herskowitz. 1991. Cell. 65:1203-1212; Fujita, A., C. Oka, Y. Arikawa, T. Katagi, A. Tonouchi, S. Kuhara, and Y. Misumi. 1994. Nature (Lond.). 372:567-570). We cloned and sequenced BUD4, which codes for a large, novel protein (Bud4p) with a potential GTP-binding motif. Bud4p is expressed and localized to the mother/bud neck in all cell types. Most mitotic cells contain two apparent rings of Bud4 immunoreactive staining, as observed for Bud3p (Chant, J., M. Mischke, E. Mitchell, I. Herskowitz, and J.R. Pringle. 1995. J. Cell Biol. 129: 767-778). Early G1 cells contain a single ring of Bud4p immunoreactive staining, whereas cells at START and in S phase lack these rings. The level of Bud4p is also regulated in a cell cycle-dependent manner. Bud4p is inefficiently localized in bud3 mutants and after a temperature shift of a temperature-sensitive mutant, cdc12, defective in the neck filaments. These observations suggest that Bud4p and Bud3p cooperate to recognize a spatial landmark (the neck filaments) during mitosis and support the hypothesis that they subsequently become a landmark for establishing the axial budding pattern in G1.

Comprehensive Identification of Cell Cycle–regulated Genes of the YeastSaccharomyces cerevisiaeby Microarray Hybridization

“…The CLB2 cluster is highly regulated with a peak in M, and the genes are very strongly induced by GAL-CLB2, whereas GAL-CLN3 appears somewhat repressive. It was previously known that four of the genes found in this cluster, CLB1, CLB2, SWI5, and BUD4, are regulated by a combination of two transcription factors, Mcm1p and SFF (Althoefer et al, 1995;Sanders and Herskowitz, 1996). Mcm1p binds to the consensus TTACCNAAT-TNGGTAA (Acton et al, 1997), whereas, on the basis of three of these genes, SFF was thought to bind to the consensus sequence GTMAACAA.…”

“…Later in the cell cycle, the Clb2p-Cdc28p complex represses the activity of SBF, returning the expression of SBF-regulated genes to low levels (Amon et al, 1993). Furthermore, Clb2p-Cdc28p is known to activate expression of at least four genes, CLB1, CLB2, SWI5, and BUD4 (Althoefer et al, 1995;Sanders and Herskowitz, 1996).…”

“…In cooperation with Ste12p, Mcm1p directs the cell cycle expression of some genes in early G1 phase (Oehlen et al, 1996). In cooperation with an uncloned factor called "Swi five factor" (SFF), it induces the expression of CLB1, CLB2, BUD4, and SWI5 in M (Lydall et al, 1991;Sanders and Herskowitz, 1996). Finally, possibly acting without a partner, it induces transcription of CLN3, SWI4, and CDC6 at the M/G1 boundary (McInerny et al, 1997).…”

The Role of Cdc42p GTPase-activating Proteins in Assembly of the Septin Ring in Yeast

“…For example, considerable evidence suggests that the septins are involved in one or more steps of vesicle trafficking in mammalian cells (Hsu et al, 1998;Beites et al, 1999;Kartmann and Roth, 2001;Dent et al, 2002). In yeast, the septins play roles in bud-site selection, the spatial organization of cell-wall deposition, and the "morphogenesis checkpoint" that couples cell-cycle progression to progress in bud formation Sanders and Herskowitz, 1996;DeMarini et al, 1997;Barral et al, 1999;Shulewitz et al, 1999;Longtine et al, 2000;Schenkman et al, 2002). Proteins involved both in cytokinesis and in these other diverse processes are targeted to the mother-bud neck in a septin-dependent manner with a variety of temporal and spatial patterns (Gladfelter et al, 2001b).…”

Cell Polarity in Saccharomyces cerevisiae Depends on Proper Localization of the Bud9 Landmark Protein by the EKC/KEOPS Complex

“…First, site selection occurs on the cell surface, a spatial landmark where cells will polarize. The bud sites during axial budding are marked with the axial landmarks Axl1p, Axl2p, Bud3p, and Bud4p (Fujita et al 1994;Halme et al 1996;Sanders and Herskowitz 1996). The bipolar landmarks Bud8p and Bud9p of the distal and proximal poles, respectively, determine the polarization axis of budding in diploid cells (Harkins et al 2001).…”