Heat shock factor 4 regulates the expression of HSP25 and alpha B-crystallin by associating with DEXD/H-box RNA helicase UAP56

Abstract

Heat shock factor 4 controls the transcription of small heat shock proteins (e.g., HSP25, alpha B-cyrstallin, and r-crystallin), that play important roles in modulating lens proteostasis. However, the molecular mechanism underlying HSF4-mediated transcription is still unclear. Using yeast two hybrid, we found that HSF4 interacts with the ATP-dependent DEXD/H-box RNA helicase UAP56, and their interaction in lens epithelial cell line was further confirmed by GST-pull down assay. UAP56 is a vital regulator of pre-mRNA splicing and mature mRNA nuclear export. The immunofluorescence assay showed that HSF4 and UBA56 colocalize with each other in the nucleus of lens epithelial cells. Ectopic UAP56 upregulated HSF4-controlled HSP25 and alpha Bcrystallin proteins expression, while knocking down UAP56 by shRNA reversed it. Moreover, UAP56 interacts with and facilitates the nuclear exportation of HSP25 and alpha B-crystallin mRNA without impacting their total mRNA expression level. In lens tissues, both UAP56 and HSF4 are expressed in the same nucleus of lens fiber cells, and their expression levels are simultaneously reduced with fiber cell maturation. Taken together, these data suggested that UAP56 is a novel regulator of HSF4 and might upregulate HSF4's downstream mRNA maturation and nuclear exportation.

HSP4 triggers epithelial‐mesenchymal transition and promotes motility capacities of hepatocellular carcinoma cells via activating AKT

“…By far, accumulating evidence has been made to confirm the significance of HSF4 in carcinogenesis process 17,18 . As a stress responsive transcription factor, HSF4 has been reported to overexpressed in several kinds of solid tumours such as colorectal tumour, 17 and was proved to be an independent indicator for prognosis.…”

“…Moreover, HSF4 was also reported to regulate several important biological function of cancer cells. For example downregulation of HSF4 was negatively correlated with the expression of p21 and p27, which could directly induce cell cycle arrest and senescence and inhibit tumour cell proliferation 17,18 . In addition, knock down of HSF4 in p53‐deficiency mice models could effectively suppress the formation of spontaneous tumours 19 .…”

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“…His-NLRP3 protein was purified from E. coli and incubated with 10 μg of purified GST or GST-NF-κB protein [17] . The GST-associated proteins were then purified using glutathione sepharose 4B, and the bound NLRP3 was detected by western blotting.…”

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“…HSF4 knockout mice had abnormal lens development and the formation of cataracts due to aberrant cellular proliferation and differentiation, partly due to the reduced γ-crystallin expression in the lens fiber cells [ 53 ]. Besides, HSF4 also participated in the maturation and nucleus exportation of crystallins and HSP25 mRNA by interacting with RNA helicase UAP56 in the lens cells [ 57 ].…”