Human immunodeficiency virus (HIV) can infect human colon epithelial cell lines by both CD4-dependent and -independent mechanisms. The present studies assessed cellular factors that are important for HIV-1 transcription in human colon epithelial cells. The HIV-1 long terminal repeat (LTR) was shown to contain functional DNA cis-regulatory elements downstream of the viral transactivator-responsive element in the transcribed noncoding 5' leader sequence. These downstream regulatory elements, termed DSE, can bind c-Fos and JunD and transmit protein kinase C activation signals to the HIV LTR. Moreover, specific Jun and Fos transcription factors can transactivate HIV-1 provirus in human colon epithelial cells. The DSE also bind related proteins of the CREB/ATF family. In this regard, the DSE behave as 12-0-tetradecanoylphorbol 13-acetate responder element-like cAMP-responsive elements because they bind both AP-1 and CREB/ATF transcription factors, thereby permitting induction of the HIV-1 LTR by both protein kinase C and A activation signals.