MBP1/YDL056W Summary Help

Standard Name MBP1 1
Systematic Name YDL056W
Feature Type ORF, Verified
Description Transcription factor; involved in regulation of cell cycle progression from G1 to S phase, forms a complex with Swi6p that binds to MluI cell cycle box regulatory element in promoters of DNA synthesis genes (1 and see Summary Paragraph)
Name Description MluI-box Binding Protein 1
Chromosomal Location
ChrIV:352877 to 355378 | ORF Map | GBrowse
Gene Ontology Annotations All MBP1 GO evidence and references
  View Computational GO annotations for MBP1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Targets 116 genes
Classical genetics
Large-scale survey
144 total interaction(s) for 95 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 9
  • Affinity Capture-RNA: 1
  • Affinity Capture-Western: 15
  • Biochemical Activity: 3
  • Co-localization: 1
  • Co-purification: 1
  • PCA: 2
  • Reconstituted Complex: 2
  • Two-hybrid: 5

Genetic Interactions
  • Dosage Growth Defect: 2
  • Dosage Rescue: 5
  • Negative Genetic: 54
  • Phenotypic Enhancement: 4
  • Phenotypic Suppression: 4
  • Positive Genetic: 16
  • Synthetic Growth Defect: 9
  • Synthetic Lethality: 3
  • Synthetic Rescue: 8

Expression Summary
Length (a.a.) 833
Molecular Weight (Da) 93,907
Isoelectric Point (pI) 10.08
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrIV:352877 to 355378 | ORF Map | GBrowse
Last Update Coordinates: 2004-02-11 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..2502 352877..355378 2004-02-11 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000002214

Mbp1p is a DNA-binding protein that forms MBF complex (Mlu1 cell cycle box [MCB] Binding Factor) with Swi6p. MBF is a sequence-specific transcription factor that regulates gene expression during the G1/S transition of the cell cycle (1, 2, 3, and 4). Several genes activated or repressed by MBF have been identified, many of which are involved in DNA synthesis and DNA repair (for example, CDC21, CDC8, and CDC9, and also G1 cyclins) (1, 5, 6, 3, and 7). Mbp1p can bind DNA directly without Swi6p. Swi6p does not bind DNA but acts as a trans-activator for MBF function (1, 8, 9). DNA footprinting studies suggest that MBF binds to DNA as a single Mbp1p/Swi6p heterodimer in an orientation-independent manner (10), with the most-often reported MCB consensus sequence bound by MBF being 5'-ACGCGT-3' (5, 11, 12, 6). See also 6, 13, 12, and 14 for variations.

Mbp1p is topologically related to winged helix-turn-helix transcription factors including Swi4p and Swi6p in S. cerevisiae; cdc10, res1, and res2 in S. pombe; and human hepatic nuclear factor 3-gamma (HNF3gamma) (10, 15). The N-terminal 112 amino acids are 50% identical to Swi4p and are sufficient to bind DNA, and the C-terminal residues 735-813 are 44% identical to Swi4p and can bind Swi6p (1, 10). The central portion of Mbp1p contains 2 ankyrin repeats separated by a short spacer region, a structure similar to that found in Swi4p (1).

mbp1 null mutants show deregulated expression of DNA synthesis genes and populations of vegetatively growing cells show a slight increase in average cell volume and budding index (7). The viability of mbp1 mutants suggests the existence of additional mechanisms for regulation of MBF target genes (1, 7). Indeed, Swi6p forms the similar SBF complex (Swi4/6 cell cycle box [SCB] Binding Factor) with Swi4p. Strains deleted for both MBP1 and SWI4 are inviable, demonstrating that SBF affects MBF-mediated transcription (1, 7). Probably owing to the extensive similarity between Mbp1p and Swi4p, these proteins show modest discrimination between their cognate binding sites in vivo (9, 13), displaying a 4-6-fold preference for their own site over that of the other transcription factor (10). However, each protein shows greater than 100-fold preference for the other's consensus sequence over non-specific sequences (10). A number of genome-wide analyses have uncovered over 100 putative targets for both MBF and SBF (13, 11, 12, 14).

Despite this apparent specificity, the presence of MCB or SCB motifs alone is not predictive of whether MBF, SBF, or both will bind to or regulate a promoter, suggesting a great complexity in the transcriptional regulation mediated through these binding sites (7). Indeed, there is physical and genetic evidence that Mbp1p interacts with Skn7p and this complex is distinct from MBF and functions in transcription regulation (16). In meiosis, MCBs can be regulated independently of Mbp1p (17).

Last updated: 2006-05-15 Contact SGD

References cited on this page View Complete Literature Guide for MBP1
1) Koch C, et al.  (1993) A role for the transcription factors Mbp1 and Swi4 in progression from G1 to S phase. Science 261(5128):1551-7
2) Koch C and Nasmyth K  (1994) Cell cycle regulated transcription in yeast. Curr Opin Cell Biol 6(3):451-9
3) Breeden L  (1996) Start-specific transcription in yeast. Curr Top Microbiol Immunol 208():95-127
4) Bahler J  (2005) Cell-cycle control of gene expression in budding and fission yeast. Annu Rev Genet 39:69-94
5) Lowndes NF, et al.  (1991) Coordination of expression of DNA synthesis genes in budding yeast by a cell-cycle regulated trans factor. Nature 350(6315):247-50
6) McIntosh EM, et al.  (1991) Characterization of a short, cis-acting DNA sequence which conveys cell cycle stage-dependent transcription in Saccharomyces cerevisiae. Mol Cell Biol 11(1):329-37
7) Bean JM, et al.  (2005) High functional overlap between MluI cell-cycle box binding factor and Swi4/6 cell-cycle box binding factor in the G1/S transcriptional program in Saccharomyces cerevisiae. Genetics 171(1):49-61
8) Lowndes NF, et al.  (1992) SWI6 protein is required for transcription of the periodically expressed DNA synthesis genes in budding yeast. Nature 357(6378):505-8
9) Dirick L, et al.  (1992) A central role for SWI6 in modulating cell cycle Start-specific transcription in yeast. Nature 357(6378):508-13
10) Taylor IA, et al.  (2000) Characterization of the DNA-binding domains from the yeast cell-cycle transcription factors Mbp1 and Swi4. Biochemistry 39(14):3943-54
11) Wolfsberg TG, et al.  (1999) Candidate regulatory sequence elements for cell cycle-dependent transcription in Saccharomyces cerevisiae. Genome Res 9(8):775-92
12) Spellman PT, et al.  (1998) Comprehensive identification of cell cycle-regulated genes of the yeast Saccharomyces cerevisiae by microarray hybridization. Mol Biol Cell 9(12):3273-97
13) Iyer VR, et al.  (2001) Genomic binding sites of the yeast cell-cycle transcription factors SBF and MBF. Nature 409(6819):533-8
14) Cho RJ, et al.  (1998) A genome-wide transcriptional analysis of the mitotic cell cycle. Mol Cell 2(1):65-73
15) Nair M, et al.  (2003) NMR structure of the DNA-binding domain of the cell cycle protein Mbp1 from Saccharomyces cerevisiae. Biochemistry 42(5):1266-73
16) Bouquin N, et al.  (1999) Association of the cell cycle transcription factor Mbp1 with the Skn7 response regulator in budding yeast. Mol Biol Cell 10(10):3389-400
17) Raithatha SA and Stuart DT  (2005) Meiosis-specific regulation of the Saccharomyces cerevisiae S-phase cyclin CLB5 is dependent on MluI cell cycle box (MCB) elements in its promoter but is independent of MCB-binding factor activity. Genetics 169(3):1329-42
18) Harbison CT, et al.  (2004) Transcriptional regulatory code of a eukaryotic genome. Nature 431(7004):99-104
19) Zhu C, et al.  (2009) High-resolution DNA-binding specificity analysis of yeast transcription factors. Genome Res 19(4):556-66
20) Badis G, et al.  (2008) A library of yeast transcription factor motifs reveals a widespread function for Rsc3 in targeting nucleosome exclusion at promoters. Mol Cell 32(6):878-87