Alternative Splicing Targeting the hTAF4-TAFH Domain of TAF4 Represses Proliferation and Accelerates Chondrogenic Differentiation of Human Mesenchymal Stem Cells

Abstract

Transcription factor IID (TFIID) activity can be regulated by cellular signals to specifically alter transcription of particular subsets of genes. Alternative splicing of TFIID subunits is often the result of external stimulation of upstream signaling pathways. We studied tissue distribution and cellular expression of different splice variants of TFIID subunit TAF4 mRNA and biochemical properties of its isoforms in human mesenchymal stem cells (hMSCs) to reveal the role of different isoforms of TAF4 in the regulation of proliferation and differentiation. Expression of TAF4 transcripts with exons VI or VII deleted, which results in a structurally modified hTAF4-TAFH domain, increases during early differentiation of hMSCs into osteoblasts, adipocytes and chondrocytes. Functional analysis data reveals that TAF4 isoforms with the deleted hTAF4-TAFH domain repress proliferation of hMSCs and preferentially promote chondrogenic differentiation at the expense of other developmental pathways. This study also provides initial data showing possible cross-talks between TAF4 and TP53 activity and switching between canonical and non-canonical WNT signaling in the processes of proliferation and differentiation of hMSCs. We propose that TAF4 isoforms generated by the alternative splicing participate in the conversion of the cellular transcriptional programs from the maintenance of stem cell state to differentiation, particularly differentiation along the chondrogenic pathway.

SETD6 controls the expression of estrogen-responsive genes and proliferation of breast carcinoma cells

“…Alternative splice variants of TAF4 lack parts of the TAF homology domain, which mediates association with a variety of transcriptional factors. These TAF4 variants are differentially expressed in adult tissues, stem cells, and differentiated cells, potentially leading to different tissue-specific gene expression patterns 44 . To investigate how SETD6 regulates the expression of estrogen-responsive genes, we have performed chromatin immunoprecipitations of stably-expressed FLAG-SETD6 and transiently overexpressed FLAG-SETD6 in MCF7 cells, but failed to detect its presence at the promoter of CDKN1A , PGR , or TFF1 (Fig.…”

A genome wide analysis of alternative splicing events during the osteogenic differentiation of human cartilage endplate-derived stem cells

“…Lately, the AS mechanism underlying stem cell differentiation has piqued people's interest. Kazantseva et al (29) reported that depletion of hTAF4-TAFH domain from TAF4 isoforms caused enhanced chondrogenic differentiation of human MSCs (29). In addition, a novel alternative trasncript-quantitative polymerase chain reaction method was created by McAlinden et al (30) to quantify isoforms of alternatively spliced Col2a1 gene, and the results indicated that the majority of ATDC5 cells were the chondroprogenitor cells induced by the standard chondrogenic differentiation method.…”

Diversity in TAF Proteomics: Consequences for Cellular Differentiation and Migration

“…Analyses of the alternative splicing of TAF4 in various mouse and human cells and tissues identified multiple and complex splicing patterns [ 86 , 87 ]. In mouse, five alternative isoforms with deletions in the functional domains result in dominant negative effects in nuclear receptor-mediated transcriptional activation [ 86 ].…”

“…In mouse, five alternative isoforms with deletions in the functional domains result in dominant negative effects in nuclear receptor-mediated transcriptional activation [ 86 ]. Complex patterns of TAF4 alternative splicing occur in different human tissues [ 87 ]. Although, a significant number of TAF4 alternatively spliced mRNAs contain a premature termination codon, indicating that these splice transcripts are subjected to the nonsense-mediated RNA decay, others preserve the open reading frame (ORF) and could be considered as possessing some functional properties in the cell.…”