The Role Of GATA4 In Gene Transcription Directed By RNA Polymerase ? And ?

GATA4 is a member of the GATA family of zinc finger transcription factors that regulate gene transcription by binding to GATA elements.GATA4 was originally discovered as a regulator of cardiac development,and GATA4 was subsequently found to be involved in the regulation of expression for various genes.In addition to regulating heart development and transcription,GATA4 plays an important role in variety of biological processes,including tumour cell proliferation.Early work in our laboratory showed that FLNA is involved in the regulation of Pol I and Pol III gene transcription and tumour cell proliferation.Recent mRNA-seq analysis result revealed that FLNA knockdown increased GATA4 mRNA expression in SaOS2 cells,suggesting that GATA4 could invole the regulation of Pol I and Pol III gene transcription.To prove this assumption,GATA4 shRNA transiently tansfected cells and GATA4 shRNA expressing stable cell lines were generated,Pol I and Pol III gene transcription were analyzed using RT-qPCR;the results showed that FLNA knockdown can inhibit Pol I and Pol III gene transcription and cell proliferation.The mechanism by which GATA4 regulates Pol I and Pol III gene transcription was investigated using the stable cell line obtained,the data showed that GATA4 knckdown inhibited the expression of Pol I-specific transcription factor RRN3 and UBF1 and the expression ofPol III-specific transcription factor BRF1 and TFIIIC2.The result from reporter assays indicated that GATA4 regulates expression of BRF1 and TFIIIC2 by affecting their promoter activities.The data from the study of interaction between SP1 and GATA4 revealed that GATA4 knockdown inhibited Sp1 expression,and vice versa.Since GATA4 promoter contains SP1 binding sites,and the activity of the promoter containing SP1 mutated sites was tested by repoerter aassay,mutation of SP1 binding sites inhibited GATA4 promoter activity,suggesting that SP1 can regulate GATA4 gene transcription.However,whether SP1 and GATA4 can coordinately moduate Pol I and Pol III gene transcription remained to be investigated.Taken together,in this project we discovered that GATA4 is required for Pol I and Pol III gene transcription,and can positively regulate cell proliferation for a number of transformed cell types.The results from this study broaden our understaning for the mechanism of Pol I and Pol III gene transcription,and provide more complete explanation for the mechanism of tumour cell proliferation mediated by GATA4.