SERPINB2 is regulated by dynamic interactions with pause-release proteins and enhancer RNAs

The SERPINB2 gene is strongly upregulated in inflammatory states. In monocytes, it can constitute up to 1% of total cellular protein. It functions in protection from proteotoxic stress and plays a role in angioedema. The purpose of this study was to define the roles of enhancer RNAs embedded in the SERPIN gene complex. We found that the upstream enhancer RNAs upregulated SERPINB2 and the enhancer RNAs were expressed prior to those of SERPINB2 mRNA. Studies of the SERPINB2 promoter demonstrated the presence of an RNA polymerase II pause-inducing protein, NELF. Stimulation with LPS led to recruitment of the pause-releasing kinase P-TEFb and departure of the pause-inducing protein NELF. RNA immunoprecipitation revealed that NELF and the CDK9 component of P-TEFb bound to the enhancer RNAs after stimulation with distinct kinetics. Knock-down of the enhancer RNAs compromised stimulus induction of promoter and enhancer chromatin changes. Conversely, over-expression was associated with enhanced recruitment of c-JUN and increased expression of SERPINB2 mRNA expression. This study is the first to associate enhancer RNAs with SERPINB2 and is the first demonstration of acquisition of NELF binding by enhancer RNAs on chromatin.