THE MOUSE THYMOSIN BETA-4 GENE - STRUCTURE, PROMOTER IDENTIFICATION, AND CHROMOSOME LOCALIZATION

Thymosin beta 4 (T beta 4) is an actin monomer sequestering protein th at may have a critical role in modulating the dynamics of actin polyme rization and depolymerization in nonmuscle cells. Its regulatory role is consistent with the many examples of transcriptional regulation of T beta 4 and of tissue-specific expression. Furthermore, lymphocytes h ave a unique T beta 4 transcript relative to the ubiquitous transcript found in many other tissues and cells. To determine how T beta 4 gene expression is regulated and how the alternative transcripts are deriv ed, we cloned the mouse T beta 4 gene. We established that there is a single mouse TP beta gene and found that the lymphoid-specific transcr ipt is generated by extending the ubiquitous exon 1 with an alternate downstream splice site. The transcription start site is defined by pri mer extension analysis, and the 5'-flanking region has many of the cha racteristics of a promoter. It is pyrimidine-rich and contains typical promoter elements, including a GC box, an initiator site, and consens us transcription factor binding sites. The mouse T beta 4 gene locus ( Ptmb4) is located by interspecific backcross mapping to the distal reg ion of the mouse X chromosome, linked to Btk and Gja6. (C) 1996 Academ ic Press, Inc.