Project description:Myocardin-related transcription factor A (MRTF-A) in complex with the serum response factor (SRF) regulates the expression of cytoskeletal genes in response to cytoplasmic and nuclear actin dynamics. Different components of nucleoskeleton, besides nuclear actin, also regulate the activity of MRTF-A. Here we extend these studies by showing that lamina-associated polypeptide 2α (Lap2α), the nucleoplasmic isoform of Lap2, is a novel regulator, and a direct binding partner of MRTF-A. Lap2α is a nucleoplasmic protein that interacts with A-type lamins and the retinoblastoma protein (pRb) and contributes to chromatin organization. Unlike other known MRTF-A regulators, Lap2α is not required for MRTF-A nucleo-cytoplasmic shuttling; it functions within the nucleus where it binds MRTF-A directly via its unique C-terminal domain prior to MRTF-A forming the complex with chromatin and SRF. Such interaction affects MRTF-A transcriptional activity since genome-wide analysis revealed reduced binding of MRTF-A to SRF target genes in Lap2α knockout cells compared to control cells that consequently led to impaired expression of target genes. Our studies therefore add another regulatory layer to the control MRTF-A-SRF-mediated gene expression, and broaden the role of Lap2α in transcriptional regulation.
Project description:Myocardin-related transcription factor A (MRTF-A) in complex with the serum response factor (SRF) regulates the expression of cytoskeletal genes in response to cytoplasmic and nuclear actin dynamics. Different components of nucleoskeleton, besides nuclear actin, also regulate the activity of MRTF-A. Here we extend these studies by showing that lamina-associated polypeptide 2α (Lap2α), the nucleoplasmic isoform of Lap2, is a novel regulator, and a direct binding partner of MRTF-A. Lap2α is a nucleoplasmic protein that interacts with A-type lamins and the retinoblastoma protein (pRb) and contributes to chromatin organization. Unlike other known MRTF-A regulators, Lap2α is not required for MRTF-A nucleo-cytoplasmic shuttling; it functions within the nucleus where it binds MRTF-A directly via its unique C-terminal domain prior to MRTF-A forming the complex with chromatin and SRF. Such interaction affects MRTF-A transcriptional activity since genome-wide analysis revealed reduced binding of MRTF-A to SRF target genes in Lap2α knockout cells compared to control cells that consequently led to impaired expression of target genes. Our studies therefore add another regulatory layer to the control MRTF-A-SRF-mediated gene expression, and broaden the role of Lap2α in transcriptional regulation.
Project description:Dysregulation of Hippo pathway results in activation of transcriptional co-activators YAP/TAZ in breast cancer. Previously, we showed that overexpression of TAZ in breast cancer promotes cell migration, invasion and tumorigenesis. Here, we show that upregulation of TAZ in breast cancers could also be due to dysregulation of TAZ transcription. Heregulin β1 (HRG1) increases TAZ mRNA level in breast cancer cells. TAZ is a direct target of MRTF/SRF transcriptional factors which are activated by HRG1. Both MRTF/SRF and TAZ are the important downstream effectors enhancing cell migration induced by HRG1. TAZ mRNA level is correlated with nuclear localization of MRTF in breast cancer cells and the mRNA level of MRTF/SRF direct target genes in breast cancers, indicating the correlation between MRTF/SRF activity and TAZ expression. Our results provide new insights into the transcriptional regulation of TAZ and dysregulation mechanism of TAZ in breast cancer, which could be a new therapeutic strategy for breast cancer.
