Transcriptional repression of autophagy and lysosome biogenesis.

Abstract

The microphthalmia/transcription factor E (MiT/TFE) family activates macroautophagy/autophagy and lysosomal genes during acute nutrient deficiency. However, the mechanisms that suppress transcription of these genes under steady-state, nutrient-rich conditions to prevent unnecessary expression remain unclear. In this study, we identified a previously unrecognized mechanism of transcriptional repression for autophagy and lysosomal genes. Under nutrient-rich conditions, USF2 (upstream transcription factor 2) binds to the coordinated lysosomal expression and regulation (CLEAR) motif, recruiting a repressive complex containing HDAC (histone deacetylase). In contrast, during nutrient deficiency, TFEB (transcription factor EB) displaces USF2 at the same motif, activating transcription. This switch is regulated by USF2 phosphorylation at serine 155 by GSK3B (glycogen synthase kinase 3 beta). Reduced phosphorylation under nutrient-deprived conditions weakens USF2's DNA binding affinity, allowing TFEB to competitively bind and activate target genes. Knockdown or knockout of Usf2 upregulates specific autophagy and lysosomal genes, leading to enhanced lysosomal functionality and increased autophagic flux. In USF2-deficient cells, the SERPINA1 Z variant/antitrypsin Z - an aggregation-prone mutant protein used as a model - is rapidly cleared via the autophagy-lysosome pathway. Therefore, modulation of USF2 activity may be a therapeutic strategy for managing diseases associated with autophagy and lysosomal dysfunction.Abbreviation: CLEAR: coordinated lysosomal expression and regulation; GSK3B: glycogen synthase kinase 3 beta; HDAC: histone deacetylase; MiT/TFE: microphthalmia/transcription factor E; NuRD: nucleosome remodeling and deacetylation; SERPINA1 Z variant/ATZ/antitrypsin Z; TFE3: transcription factor E3; TFEB: transcription factor EB; USF2: upstream transcription factor 2.