Transcription elongation regulator 1, also known as TCERG1, is a protein which in humans is encoded by the TCERG1 gene.

This gene encodes a nuclear protein that regulates transcriptional elongation and pre-mRNA splicing. The encoded protein interacts with the hyperphosphorylated C-terminal domain of RNA polymerase II via multiple FF domains, and with the pre-mRNA splicing factor SF1 via a WW domain. Alternative splicing results in multiple transcripts variants encoding different isoforms. [provided by RefSeq, Jul 2008].
Function: Transcription factor that binds RNA polymerase II and inhibits the elongation of transcripts from target promoters. Regulates transcription elongation in a TATA box-dependent manner. Necessary for TAT-dependent activation of the human immunodeficiency virus type 1 (HIV-1) promoter.