 . 13: 1409–1421 (1997) S accharomyces carlsbergensis Contains Two Functional Genes Encoding the Acyl-CoA Binding Protein, one Similar to the ACB1 Gene from S . cerevisiae and one Identical to the ACB1 Gene from S. monacensis CLAUS BØRSTING 1 *, RENE HUMMEL 1 , EMILY R. SCHULTZ 2 , TIMOTHY M. ROSE 2 , MOGENS B. PEDERSEN 3 , JENS KNUDSEN 4 AND KARSTEN KRISTIANSEN 1 1 Department of M olecular Biology and 4 Institute of Biochemistry, Odense University, Campusvej 55, DK-5230 Odense M . Denmark 2 Department of Pathobiology, School of Public Health and Community M edicine, University of W ashington, Seattle, WA 98195, U.S.A. 3 Carlsberg Research Laboratory, Gamle Carlsberg vej 10, DK-2500 Copenhagen Valby, Denmark Received 9 November 1996; accepted 15 May 1997 S accharomyces carlsbergensis is an amphiploid, and it has previously been suggested that the genomes of S. carlsbergensis originate from S . cerevisiae and S. monacensis. We have cloned the ACB1 genes encoding the acyl-CoA binding protein (ACBP) from S . carlsbergensis, S . cerevisiae and S. monacensis. Two genes were found in S . carlsbergensis and named ACB1 type 1 and type 2, respectively. The type 1 gene is identical to the S . cerevisiae ACB1 gene except for three substitutions, one single base pair deletion and one double base pair insertion, all located in the promoter region. The type 2 gene is completely identical to the S. monacensis ACB1 gene. These findings substantiate the notion that S . carlsbergensis is a hybrid between S . cerevisiae and S. monacensis. Both ACB1 type 1 and type 2 are actively transcribed in S . carlsbergensis and transcription is initiated at sites identical to those used for transcriptional initiation of the ACB1 genes in S . cerevisiae and S. monacensis, respectively. Two polyadenylation sites, spaced 225 bp apart, are present in the S. cerevisiae ACB1 gene. The upstream polyadenylation site is used exclusively during exponential growth, whereas both sites are utilized during later stages of growth. All sequence information is listed under EMBL Accession Numbers Y08687, Y08688, Y08689 and Y08690.  1997 John Wiley & Sons, Ltd. Yeast 13: 1409–1421, 1997. No. of Figures: 5. No. of Tables: 0. No. of References: 53   — acyl-CoA binding protein; ACB1; Saccharomyces cerevisiae; Saccharomyces carlsbergensis; Saccharomyces monacensis; brewing yeasts; hybrid yeast INTRODUCTION One of the yeast strains most frequently used in modern beer making is the bottom fermenting strain S accharomyces carlsbergensis, first isolated and named by E. C. Hansen (1908) at the Carlsberg laboratory. The name S . carlsbergensis was later replaced by the name S. pastorianus (Vaughan-Martini and Martini, 1987); however, for practical reasons we use the conventional name S. carlsbergensis throughout this article (for a discussion see Kielland-Brandt et al., 1995). Single chromosome transfer of chromosomes from S . carlsbergensis to S . cerevisiae has shown that the S . carlsbergensis genome holds two differ- ent chromosomes III, V and XII (Nilsson-Tillgren et al., 1981, 1986; Holmberg, 1982; Petersen et al., 1987) and three different chromosomes X and XIII *Correspondence to: Claus Børsting, Department of Molecular Biology, Odense University, Campusvej 55, DK-5230 Odense M, Denmark. Tel: (+45) 65 57 24 10; fax: (+45) 65 93 27 81; e-mail: borsting@biobase.dk. Contract grant sponsor: Danish Natural Science Research Council. Contract grant sponsor: Albani Foundation. CCC 0749–503X/97/151409–13 $17.50  1997 John Wiley & Sons, Ltd.