SP4(Sp4 transcription factor), also known as Transcription factor Sp4, MGC130008, MGC130009, SPR-1, HF1B, is a protein that in humans is encoded by the SP4 gene. It is a multigene family of SP proteins. Northern blot analysis that SP4 is abundantly expressed as a 7.5-kb message in brain, but barely detectable in other human cell lines. SP4 is an activator protein like SP1. However, in contrast to SP1, SP4 is not able to act synergistically through adjacent binding sites.