Stage specific element for germ-line transcription of the TCR receptor α gene

We explored the a stage specific element for germ-line (GL) transcription of the TCR-a gene which is closely associated with its gene rearrangement. GL transcription of the TCR-a gene including the first segment of the Ja locus, Ja49, was delayed compared to that of the TCR-b gene in both normal and TCR-Tg mice. in TCR-Tg, the endogenous Ja49 GL transcript could not yet be detected at the CD25+ DN stage when the TCR-a transgene was expressed. In T cell hybridomas of either DN or immature CD8SP thymocytes, only the latter expressed the Ja49 GL. The upstream region of the Ja49 contains promoter activity in immature CD8SP cells but not in DN stage ones. These indicate that the Ja49 GL transcription occurs only at a specific developing stage, which is regulated by a cis-element located within the Ja49 locus other than Ea.