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E3 ubiquitin ligase UBR5 modulates circadian rhythm by facilitating the ubiquitination and degradation of the key clock transcription factor BMAL1

ABSTRACT: The circadian clock governs the intrinsic rhythm of biological activities and is regulated by an autonomous molecular clock, maintaining approximately 24-hour oscillations. BMAL1, as a pivotal component of the circadian clock, is subject to degradation via the ubiquitin-proteasome system (UPS). However, limited information exists regarding UPS enzymes that intricately control both BMAL1 stability and transcriptional activity, thereby influencing cellular circadian rhythms. In this study, we identify and validate UBR5 as a novel E3 ubiquitin ligase that interacts with BMAL1 using affinity purification, mass spectrometry, and biochemical assays. Overexpression of UBR5 promotes BMAL1 ubiquitination, leading to decreased stability and protein levels of BMAL1, consequently dampening its transcriptional activity. Conversely, UBR5 knockdown elevates BMAL1 protein levels. Domain mapping reveals that the C-terminus of BMAL1 interacts with the N-terminal domains of UBR5. Similarly, experiments using Drosophila clock system demonstrate that HYD, the Drosophila homolog of UBR5, interacts with and downregulates CYCLE, the Drosophila homolog of BMAL1. PER2-luciferase reporter assays in mammalian cells and behavioral experiments in Drosophila indicate that UBR5 or hyd knockdown significantly shortens the circadian clock period. Thus, our findings unveil UBR5 as a novel regulator of BMAL1 stability and circadian rhythms, elucidating the underlying molecular mechanisms. This study adds a new layer of complexity to the regulatory network of the circadian clock at the post-translational modification level, providing potential insights into modulating dysregulated circadian rhythms.

ORGANISM(S): Homo Sapiens

SUBMITTER: Guoqiang Xu

PROVIDER: PXD050794 | iProX | Wed Mar 20 00:00:00 GMT 2024

REPOSITORIES: iProX

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E3 ubiquitin ligase UBR5 modulates circadian rhythm by facilitating the ubiquitination and degradation of the key clock transcription factor BMAL1

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