The long terminal repeat binding protein-1 (LBP-1) mammalian family of transcription factors are proteins that stimulate transcription in HeLa cells from the major late promoter of simian virus 40 in vitro. The two related human LBP-1 genes are TFCP2A, which encodes the alternatively spliced transcripts LBP-1a and LBP-1b, and TFCP2C, which encodes LBP-1c and LBP-1d. LBP-9, also designated transcription factor CP2-like 1 (TFCP2L1), is a protein of 479 amino acids. LBP-9 shows 83% sequence homology with LBP-1b and acts as a suppressor factor inhibiting the stimulation effect of LBP-1b. LBP-9 may regulate the P450scc reporter activity through the -155/-131 element.