Identification of GTF2IRD 1, a putative transcription factor within the Williams-Beuren syndrome deletion at 7q11.23

Williams-Beuren syndrome (WBS) is a microdeletion syndrome caused by haploinsufficiency of genes at 7q11.23, Here we describe the identification and characterization of a novel gene named GTF2IRD1, for GTF2I-repeat domain I,within the WBS deletion region. Northern blot analysis revealed ubiquitous expression during development with two transcripts of 3.6 kb and 5.0 kb generated by alternative splicing. GTF2IRD1 encodes a protein of 944 amino acids that contains a region of high similarity to a unique motif with helix-loop-helix forming potential occurring within the transcription factor GTF2I. Analogous to TFII-I, the product of GTF2IRD1 may have the ability to interact with other HLH-proteins and function as a transcription factor or as a negative transcriptional regulator. A recent report of the identification of a muscle-specific transcription factor, MusTRD1 supports this hypothesis (O'Mahoney et al., 1998). The open reading frame described for MusTRD1 is identical to that of GTF2IRD1; however, the putative MusTRD1-protein is 486 amino acids shorter than the predicted protein encoded by GTF2IRD1. A heterozygous deletion of GTF2IRD1 may contribute to the complex WBS phenotype.