Biology subjects

Cliff Zhang, Q.

Publications and source records attributed to Cliff Zhang, Q..

3 recordsLinked to original sources

bioRxiv2023

Structural RNA components supervise the sequential DNA cleavage in R2 retrotransposon

Retroelements are the widespread jumping elements considered as major drivers for genome evolution, which can also be repurposed as gene-editing tools. Here, we determined the cryo-EM structures of eukaryotic R2 retrotransposon with ribosomal DNA target and regulatory RNAs. Combined with biochemical and sequencing analysis, we revealed two essential DNA regions, Drr and Dcr, required for R2 recognition and cleavage. The association of 3 regulatory RNA with R2 protein accelerates the first-strand cleavage, blocks the second-strand cleavage, and initiates the reverse transcription starting from the polyA tail. Removing 3 regulatory RNA by reverse transcription allows the association of 5 regulatory RNA and initiates the second-strand cleavage. Our work explained the DNA recognition and supervised sequential retrotransposition mechanisms by R2 machinery, providing novel insights into the retrotransposon and application reprogramming.

molecular biology↗

bioRxiv2022

Structural Insights into Branch Site Proofreading by Human Spliceosome

Selection of the pre-mRNA branch site (BS) by U2 snRNP is crucial to prespliceosome (A complex) assembly. The RNA helicase PRP5 proofreads BS selection; but the underlying mechanism remains unclear. Here we report the atomic structures of two sequential complexes leading to prespliceosome assembly: human 17S U2 snRNP and a cross-exon pre-A complex. PRP5 is anchored on 17S U2 snRNP mainly through occupation of the RNA path of SF3B1 by an acidic loop of PRP5; the helicase domain of PRP5 associates with U2 snRNA; the BS-interacting stem loop (BSL) of U2 snRNA is shielded by the splicing factor TAT-SF1, unable to engage the BS. In the pre-A complex, an initial U2/BS duplex is formed; the translocated helicase domain of PRP5 stays with U2 snRNA; the acidic loop still occupies the RNA path. The pre-A conformation is specifically stabilized by the splicing factors SF1, DNAJC8 and SF3A2. Cancer-derived mutations in SF3B1 damage its association with PRP5, compromising BS proofreading. Together, these findings reveal key insights into prespliceosome assembly and BS selection/proofreading by PRP5.

biochemistry↗

bioRxiv2021

The chromatin-remodeling enzyme Smarca5 regulates erythrocyte aggregation via Keap1-Nrf2 signaling

Although thrombosis has been extensively studied using various animal models, however, our understanding of the underlying mechanism remains elusive. Here, using zebrafish model, we demonstrated that smarca5-deficient red blood cells (RBCs) formed blood clots in the caudal vein plexus that mimics venous thrombosis. We further used the anti-thrombosis drugs to treat smarca5zko1049a embryos and found that a thrombin inhibitor, argatroban, partially prevented blood clot formation in smarca5zko1049a. To explore the regulatory mechanism of smarca5 in RBC homeostasis, we profiled the chromatin accessibility landscape and transcriptome features in RBCs from smarca5zko1049a and their siblings and found that both the chromatin accessibility at the keap1a promoter and expression of keap1a were decreased. Keap1 is a suppressor protein of Nrf2, which is a major regulator of oxidative responses. We further identified that the expression of hmox1a, a downstream target of Keap1-Nrf2 signaling pathway, was markedly increased upon smarca5 deletion. Importantly, overexpression of keap1a or knockdown of hmox1a partially rescued the blood clot formation, suggesting that the disrupted Keap1-Nrf2 signaling is responsible for the venous thrombosis-like phenotypes in smarca5 mutants. Together, our study using zebrafish smarca5 mutants not only characterizes a novel role for smarca5 in blood clot formation, but also provides a new venous thrombosis animal model to support drug screening and pre-clinical therapeutic assessments to treat thrombosis.

developmental biology↗