Transcription factors are required for the initiation of transcription. They regulate transcription by binding to DNA at specific nucleotide sequences within promoters and enhancers. Transcription factors, which may also bind to RNA polymerase or to other transcription factors, are involved in the preinitiation complex formation. Upstream transcription factors and inducible transcription factors bind upstream of the initiation site to repress or stimulate transcription. Upstream factors are unregulated, while inducible factors require inhibition or activation. GPBP1L1 (GC-rich promoter binding protein 1-like 1), also known as vasculin-like protein 1 or SP192, is a 474 amino acid protein belonging to the vasculin family. Localizing to nucleus, GPBP1L1 may function as a transcription factor. The gene encoding GPBP1L1 maps to human chromosome 1p34.1 and mouse chromosome 4 D1.