Association of a protein phosphatase 1 activity with the human factor C1 (HCF) complex

We have screened a human cDNA expression library with a digoxygenin-labelle d protein phosphatase 1 (PP1) probe to identify novel PP1 interacting prote ins. Eleven cDNA clones were isolated, which included genes encoding two pr eviously characterised and six novel PP1 binding proteins. Three of the cDN As encoded a protein called host cell factor (HCF), which is an essential c omponent of the cellular complex required for the transcription of the herp es simplex virus (HSV) immediate-early (IE) genes. We demonstrate that HCF and PP1 exist as a complex in nuclear extracts and that this complex is dis tinct from the form of HCF that associates with HSV VP16, The data suggest novel roles for HCF and PP1, which may be relevant to their functions in tr anscription and cell cycle progression.