Our laboratory is interested in post-transcriptional regulation. Currently we study miRNA synthesis and function in the sickle cell disease model. Clinical consequences of this genetic illness lead to a spectrum of circulatory and respiratory symptoms originating from a single mutation of the beta-globin gene. In particular pulmonary hypertension results from the vascular occlusion caused by the abnormal red blood cell shape. This leads to expression of vasoactive cytokines and hormones which aggravate and prolong the original vascular insult. Plasminogen activator inhibitor-1 (SERPINE1) and endothelin 1 (EDN1) are two such cell modulators that are dysregulated in acute phases of the illness. We identified miRNAs which are responsible for reversing expression of both SERPINE1 and EDN1; more importantly, we examined in detail the transcriptional regulation and synthesis of these key miRNA mediators. This information has been useful in that we identified a potential pharmacologic therapy that induced specific miRNA expression for the purpose of reducing the expression of SERPINE1 and EDN1.
The second area of interest examines the biological significance of protein arginine methylation of translation initiation factors. We are currently studying the effect of Arg362 methylation of factor eIF4A. The latter is the prototype of DEXD/H box nucleotide dependent helicases. We have found that methylation of Arg362 results in 1) significantly reduced ATPase activity and 2) inhibition of eIF4A assembly with eIF4G into the eIF4F heterotrimer. We believe this example of covalent modification is representative of a previously unknown regulatory circuit for modulating cellular protein synthesis. Our current efforts are directed towards identifying regulators of protein methylation and further examination of eIF4A with respect to mRNA specific effects in protein synthesis.