CHRONIC HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INFECTION STIMULATES DISTINCT NF-KAPPA-B REL DNA-BINDING ACTIVITIES IN MYELOMONOBLASTIC CELLS/

The relationship between human immunodeficiency virus type 1 (HIV-1) i nfection and the induction of NF-KB binding activity was examined in a myeloid cell model of HIV-1 infection derived from the PLB-985 cell l ine. Chronic infection of PLB-985 cells led to increased monocyte-spec ific surface marker expression, increased c-fms gene transcription, an d morphological alterations consistent with differentiation along the monocytic pathway. PLB-IIIB cells displayed a constitutive NF-kappaB-l ike binding activity that was distinct from that induced by tumor necr osis factor alpha or phorbol 12-myristate 13-acetate treatment of the parental PLB-985 cell line. This unique DNA binding activity consisted of proteins of 70, 90, and 100 kDa with a high degree of binding spec ificity for the NF-kappaB site within the PRDII domain of beta interfe ron. In this report, we characterize the nature of these proteins and demonstrate that binding of these proteins is also induced following S endai paramyxovirus infection. The 70-kDa protein corresponds to the N F-kappaB RelA (p65) subunit, which is activated in response to an acut e paramyxovirus infection or a chronic HIV-1 infection. Virus infectio n does not appear to alter the amount of RelA (p65) or NFKB1 (p50) but rather affects the capacity of IkappaBalpha to sequester RelA (p65), therefore leading to constitutive levels of RelA DNA binding activity and to increased levels of NF-kappaB-dependent gene activity. The vira lly induced 90- to 100-kDa proteins have a distinct binding specificit y for the PRDII domain and an AT-rich sequence but do not cross-react with NF-kappaB subunit-specific antisera directed against NFKB1 (p105 or p50), NFKB2 (p100 or p52), RelA (p65), or c-rel. DNA binding of the 90- to 100-kDa proteins was not inhibited by recombinant IkappaBalpha /MAD-3 and was resistant to tryptic digestion, suggesting that these p roteins may not be NF-kappaB related. Transient cotransfection experim ents demonstrated that RelA and NFKB1 expression maximally stimulated HIV-1 LTR- and NF-KB-dependent reporter genes; differences in NF-kappa B-like binding activity were also reflected in higher constitutive lev els of NF-kappaB-regulated gene expression in HIV-1-infected myeloid c ells.