title: Activating transcription factor 1 and cyclic AMP response element modulator can modulate the activity of the immunoglobulin kappa 3' enhancer.
abstract: Previously we determined that the immunoglobulin kappa 3' enhancer (kappa E3') contains at least two functional DNA sequences (PU.1/NF-EM5 and E2A) within its 132-base pair active core. We have determined that the activities of these two sequences are insufficient to account for the entire activity of the 132-base pair core. Using site-directed linker scan mutagenesis across the core fragment we identified several additional functional sequences. We used one of these functional sequences to screen a lambda gt11 cDNA expression library resulting in the isolation of cDNA clones encoding the transcription factors ATF-1 (activating transcription factor) and CREM (cyclic AMP response element modulator). Because ATF-1 and CREM are known to bind to cAMP response elements (CRE), this functional sequence was named the kappa E3'-CRE. We show that dibutyryl cAMP can increase kappa E3' enhancer activity, and in transient expression assays ATF-1 caused a 4-5-fold increase in the activity of the core enhancer while CREM-alpha expression resulted in repression of enhancer activity. RNA analyses showed increased levels of ATF-1 mRNA during B cell development and some changes in CREM transcript processing. By joining various fragments of the kappa E3' enhancer to the kappa E3'-CRE, we observed that the kappa E3'-CRE can synergistically increase transcription in association with the PU.1/NF-EM5 binding sites, suggesting a functional interaction between the proteins that bind to these DNA sequences. Consistent with this possibility, we found that ATF-1 and CREM can physically interact with PU.1. The isolation of activator and repressor proteins that bind to the kappa E3'-CRE may relate to previous conflicting results concerning the role of the cAMP signal transduction pathway in kappa gene transcription.
authors.affiliation: Department of Animal Biology, University of Pennsylvania, School of Veterinary Medicine, Philadelphia 19104, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Pongubala
authors.forename: M L
authors.initials: ML
authors.lastname: Atchison
mesh_terms: D051697:Activating Transcription Factor 1; D001402:B-Lymphocytes / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D051786:Cyclic AMP Response Element Modulator; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D008969:Molecular Sequence Data; D012097:Repressor Proteins; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*
chemical_list: D051697:Activating Transcription Factor 1; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D007145:Immunoglobulin kappa-Chains; D012097:Repressor Proteins; D014157:Transcription Factors; D051786:Cyclic AMP Response Element Modulator; D000242:Cyclic AMP