Cigarette smoke induces MUC5AC protein expression through the activation of Sp1.
Cigarette smoke (CS) exposure is associated with increased mucus production and chronic obstructive pulmonary disease (COPD). MUC5AC is the major inducible mucus gene in the airway. The purpose of this investigation was to elucidate the mechanisms of CS-induced activation of MUC5AC gene transcription. We observed that the region -3724/-3224 of the MUC5AC promoter is critical for CS-induced gene transcriptional activity and that this region contains two Sp1 binding sites. Using a lung-relevant model, we observed that CS increased nuclear Sp1 protein expression. Consequently, CS exposure resulted in enhanced Sp1-DNA binding activity and Sp1 trans-activation. Co-transfection of the MUC5AC-luc reporter with Sp1 expression plasmids resulted in significantly increased MUC5AC-luc activity, whereas co-treatment with mithramycin A, a Sp1 inhibitor, abolished CS-induced MUC5AC promoter activity. Using mobility shift assay and chromatin immunoprecipitation, we demonstrated that two Sp1 binding sites in the MUC5AC promoter are functional and responsive to CS exposure. A mutation of either Sp1 binding site in the MUC5AC promoter significantly decreased CS-induced promoter activity. Together, these data indicate that CS induces MUC5AC gene transcription predominantly through increased Sp1 nuclear protein levels and increased Sp1 binding to its promoter region.
Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15219, USA. peterdi@pitt.edu
Y Peter
YP
Di
Jinming
J
Zhao
Richart
R
Harper
D002460:Cell Line; D005260:Female; D006801:Humans; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D008297:Male; D055271:Mucin 5AC / Q000096:biosynthesis* / Q000235:genetics; D009154:Mutation; D008926:Plicamycin / Q000031:analogs & derivatives / Q000494:pharmacology; D029424:Pulmonary Disease, Chronic Obstructive / Q000209:etiology / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020218:Response Elements; D012907:Smoking / Q000009:adverse effects*; D016329:Sp1 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
C524678:MUC5AC protein, human; D055271:Mucin 5AC; D016329:Sp1 Transcription Factor; C066851:mithramycin A; D008926:Plicamycin