title: Basic helix-loop-helix transcription factor heterocomplex of Yas1p and Yas2p regulates cytochrome P450 expression in response to alkanes in the yeast Yarrowia lipolytica.
abstract: The expression of the ALK1 gene, which encodes cytochrome P450, catalyzing the first step of alkane oxidation in the alkane-assimilating yeast Yarrowia lipolytica, is highly regulated and can be induced by alkanes. Previously, we identified a cis-acting element (alkane-responsive element 1 [ARE1]) in the ALK1 promoter. We showed that a basic helix-loop-helix (bHLH) protein, Yas1p, binds to ARE1 in vivo and mediates alkane-dependent transcription induction. Yas1p, however, does not bind to ARE1 by itself in vitro, suggesting that Yas1p requires another bHLH protein partner for its DNA binding, as many bHLH transcription factors function by forming heterodimers. To identify such a binding partner of Yas1p, here we screened open reading frames encoding proteins with the bHLH motif from the Y. lipolytica genome database and identified the YAS2 gene. The deletion of the YAS2 gene abolished the alkane-responsive induction of ALK1 transcription and the growth of the yeast on alkanes. We revealed that Yas2p has transactivation activity. Furthermore, Yas1p and Yas2p formed a protein complex that was required for the binding of these proteins to ARE1. These findings allow us to postulate a model in which bHLH transcription factors Yas1p and Yas2p form a heterocomplex and mediate the transcription induction in response to alkanes.
authors.affiliation: Department of Biotechnology, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan.
authors.forename: Setsu
authors.initials: S
authors.lastname: Endoh-Yamagami
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Hirakawa
authors.forename: Daisuke
authors.initials: D
authors.lastname: Morioka
authors.forename: Ryouichi
authors.initials: R
authors.lastname: Fukuda
authors.forename: Akinori
authors.initials: A
authors.lastname: Ohta
mesh_terms: D000473:Alkanes / Q000494:pharmacology*; D000483:Alleles; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004271:DNA, Fungal / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005800:Genes, Fungal; D007294:Inositol / Q000096:biosynthesis; D008957:Models, Genetic; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects; D025062:Yarrowia / Q000187:drug effects* / Q000201:enzymology* / Q000254:growth & development
chemical_list: D000473:Alkanes; D051792:Basic Helix-Loop-Helix Proteins; D003577:Cytochrome P-450 Enzyme System; D004271:DNA, Fungal; D005656:Fungal Proteins; D007294:Inositol; D050505:Mutant Proteins