GENOMIC ORGANIZATION AND CHROMOSOMAL LOCALIZATION OF THE GENE TCF15 ENCODING THE EARLY MESODERMAL BASIC HELIX-LOOP-HELIX FACTOR BHLH-EC2

bHLH-EC2 is a recently characterized member of a growing family of bas ic helix-loop-helix transcription factors, This family includes bHLH f actors such as twist, which appear to be primarily involved in early m esodermal differentiation, and bHLH factors such as TAL-1, which have been characterized through their association with chromosomal breakpoi nts associated with T-cell leukemias. To provide for studies aimed at understanding the genetic regulation of bHLH-EC2, we have characterize d the organization of this gene and conducted preliminary studies of t he transcriptional activity of the upstream promoter region. The mouse bHLH-EC2 gene was found to consist of two exons separated by a 5-kb i ntron, an organization pattern similar to the mouse twist gene. The tr anscription initiation site was identified by RNase protection assay a nd primer extension analysis. Linked promoter-reporter gene transfecti on experiments in cultured cells indicated that while the identified u pstream sequence can function to promote transcription, it does not fu nction in a cell-specific fashion, To investigate the possible associa tion of bHLH-EC2 with hematological malignancy, the chromosomal locati on of this gene in the human was mapped by fluorescence in situ hybrid ization and assigned to chromosome band 20p13. (C) 1995 Academic Press , Inc.