Chicken ovalbumin upstream promoter transcription factor (COUP-TF)-interacting proteins 1 and 2 [CTIP1/Evi9/B cell leukaemia (Bcl) l1a and CTIP2/Bcl11b respectively] are highly related C2H2 zinc finger proteins that are abundantly expressed in brain and the immune system, and are associated with immune system malignancies. A selection procedure was employed to isolate high-affinity DNA binding sites for CTIP1. The core binding site on DNA identified in these studies, 5′-GGCCGG-3′ (upper strand), is highly related to the canonical GC box and was bound by a CTIP1 oligomeric complex(es) in vitro. Furthermore, both CTIP1 and CTIP2 repressed transcription of a reporter gene harbouring a multimerized CTIP binding site, and this repression was neither reversed by trichostatin A (an inhibitor of known class I and II histone deacetylases) nor stimulated by co-transfection of a COUP-TF family member. These results demonstrate that CTIP1 is a sequence-specific DNA binding protein and a bona fide transcriptional repressor that is capable of functioning independently of COUP-TF family members. These findings may be relevant to the physiological and/or pathological action(s) of CTIPs in cells that do not express COUP-TF family members, such as cells of the haematopoietic and immune systems.
- transcriptional repression
↵1 Present address: Center for Cell Biology and Cancer Research, Albany Medical College, 47 New Scotland Avenue, MC-165, Albany, NY 12208, U.S.A.
Abbreviations used: Bcl, B cell leukaemia; CAT, chloramphenicol acetyltransferase; COUP-TF, chicken ovalbumin upstream promoter transcription factor; CTIP, COUP-TF-interacting protein; EMSA, electrophoretic mobility shift assay; GST, glutathione S-transferase; HEK, human embryonic kidney; NP40, Nonidet P40; RE, response element; tk, thymidine kinase gene; TSA, trichostatin A; ZNF3 (etc.), zinc finger 3 (etc.).
- The Biochemical Society, London ©2002