Abstract
Transcriptional profiling of cardiac genome during hypertrophy identified two categories of genes with distinct modes of regulation. The first set of genes involved in the cells essential functions (e.g. RNA splicing) and whose transcription is expected to be incremental and contribute to the increasing cardiac mass is regulated by promoter clearance of RNA polymerase II (pol II). On the other hand, the second set that include genes with specialized function and show a robust increase in expression upon growth stimulus (cytoskeletal, extracellular matrix) are regulated by de novo pol II recruitment to promoters. Our goal was to identify the transcriptional mechanisms that distinguish these two sets of genes and then to selectively inhibit those that participate in contractile dysfunction, while preserving the expression of genes necessary for essential functions. General Transcription factor IIB (GTF2B), is one of the essential components of transcription machinery and is required for pol II recruitment. Thus, we hypothesized that inhibition of GTF2B would result in inhibition of only the specialized genes, sparing the essential genes. Our in vitro results with shRNA mediated inhibition of GTF2B in hypertrophying neonatal myocytes showed decreased expression of genes that required de novo pol II recruitment for transcription (eg. ACTA1), while no change was observed in the genes regulated by promoter clearance of pol II (Vdac1). Similarly, preliminary results with in vivo knockdown of GTF2B (~80% reduction in mRNA and ~36% in protein) via intravenous injection of modified antisense oligo in mice subjected to transaortic coarctation (TAC) showed inhibition of only cardiomyopathy-related genes that require pol II recruitment (ANF), while expression of essential genes (Vdac1) remained unchanged. Inhibition of GTF2B restricted increase in TAC-induced heart wt to 9%, compared to 29% in TAC hearts with control oligo. Echocardiography showed partial normalization of ejection fraction with GTF2B inhibitor during TAC from 61.5% to 66.4% compared to sham hearts with 71%. Thus, we conclude that by targeting GTF2B we can selectively restrict the expression of detrimental genes during hypertrophy, thereby delaying the onset of cardiac dysfunction and failure
Published Version
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