InterPro domain: IPR036887

The APSES (ASM-1, Phd1, StuA, EFG1, and Sok2) domain is a ~110-residue sequence-specific DNA-binding domain found in a family of fungal transcription factors and other DNA-binding proteins. The APSES domain is found associated with ankyrin repeats (see PDOC50088 , IPR002110 ) and a heterodimerization domain [ 1 , 2 ].

The APSES domain consists of a six-stranded beta-sheet segment folded against two pairs of alpha-helices in the topology of the winged helix-turn-helix (HTH) family of proteins [ 3 ]. The alphaA/alphaB helical pair corresponds to the HTH motif [ 4 , 4 , 5 ]. Some proteins known to contain an APSES domain are listed below:

• Saccharomyces cerevisiae (Baker's yeast) Mlu-1 box binding protein (MBP1, P39678 ); Mlu-1 and Swi6 together make up the transcription factor complex MBF (Mlu-1-binding factor), which binds to the Mlu1 cell-cycle box (MCB) elements found in the promoters of many DNA synthesis genes [ 6 ].
• Schizosaccharomyces pombe (Fission yeast) cell division cycle-related proteins res1/sct1 ( P33520 ) and res2/pct1 ( P41412 ), which are homologous to MBP1.
• S. pombe start control protein cdc10 ( P01129 ).
• Emericella nidulans (Aspergillus nidulans) cell pattern formation-associated protein stuA ( P36011 ). It regulates the transformation of undifferentiated hyphal elements into a complex multicellular structure.
• S. cerevisiae transcription factor PHD1 ( P36093 ).
• S. cerevisiae protein SOK2 ( P53438 ). It represses the transition from unicellular growth to pseudohyphae.
• Candida albicans (Yeast) enhanced filamentous growth protein (EFG1, P43064 )).
• Neurospora crassa ascospore maturation 1 protein (Asm-1, Q92251 ). It has a role in spore maturation.
• S. pombe bouquet formation protein 4 ( O60158 ), which is a nuclear membrane protein that connects telomeres to the nuclear envelop (NE) during both vegetative growth and meiosis. Bqt4 does not seem to bind DNA, but acts as an adaptor between Bqt3 and Rap1 [ 6 ].

1. Asm-1+, a Neurospora crassa gene related to transcriptional regulators of fungal development. Genetics 144, 991-1003
2. StuAp is a sequence-specific transcription factor that regulates developmental complexity in Aspergillus nidulans. EMBO J. 16, 5710-21
3. Crystal structure of the DNA-binding domain of Mbp1, a transcription factor important in cell-cycle control of DNA synthesis. Structure 5, 349-58
4. The X-ray structure of the DNA-binding domain from the Saccharomyces cerevisiae cell-cycle transcription factor Mbp1 at 2.1 A resolution. J. Mol. Biol. 272, 1-8
5. NMR structure of the DNA-binding domain of the cell cycle protein Mbp1 from Saccharomyces cerevisiae. Biochemistry 42, 1266-73
6. Membrane proteins Bqt3 and -4 anchor telomeres to the nuclear envelope to ensure chromosomal bouquet formation. J. Cell Biol. 187, 413-27