HP1α is a chromatin crosslinker that controls nuclear and mitotic chromosome mechanics
- Princeton University, United States
- Northwestern University, United States
- Massachusetts Institute of Technology, United States
- Feinberg School of Medicine, Northwestern University, United States
- University of Massachusetts Amherst, United States
- The Fred Hutchinson Cancer Research Center, United States
Abstract
Chromatin, which consists of DNA and associated proteins, contains genetic information and is a mechanical component of the nucleus. Heterochromatic histone methylation controls nucleus and chromosome stiffness, but the contribution of heterochromatin protein HP1α (CBX5) is unknown. We used a novel HP1α auxin-inducible degron human cell line to rapidly degrade HP1α. Degradation did not alter transcription, local chromatin compaction, or histone methylation, but did decrease chromatin stiffness. Single-nucleus micromanipulation reveals that HP1α is essential to chromatin-based mechanics and maintains nuclear morphology, separate from histone methylation. Further experiments with dimerization-deficient HP1αI165E indicate that chromatin crosslinking via HP1α dimerization is critical, while polymer simulations demonstrate the importance of chromatin-chromatin crosslinkers in mechanics. In mitotic chromosomes, HP1α similarly bolsters stiffness while aiding in mitotic alignment and faithful segregation. HP1α is therefore a critical chromatin-crosslinking protein that provides mechanical strength to chromosomes and the nucleus throughout the cell cycle and supports cellular functions.
Data availability
We have provided the RNAseq data sets in the supplemental material as excel files
Article and author information
Author details
Clifford P Brangwynne
Funding
National Institutes of Health (U54DK107980)
- John F Marko
National Institutes of Health (U01DA040583)
- Mark Groudine
National Institutes of Health (1UM1HG011536)
- John F Marko
- Andrew D Stephens
National Institutes of Health (R00GM123195)
- Andrew D Stephens
National Institutes of Health (U54CA193419)
- John F Marko
National Institutes of Health (U01 DA040601)
- Clifford P Brangwynne
Mark Foundation For Cancer Research (Life science research foundation Postdoctoral Fellowship,AWD1006303)
- Amy R Strom
National Institutes of Health (GM114190)
- Edward J Banigan
National Institutes of Health (R24DK106766)
- Feng Yue
National Institutes of Health (1R35GM124820)
- Feng Yue
National Institutes of Health (R01HG009906)
- Feng Yue
National Institutes of Health (U01CA200060)
- Feng Yue
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2021, Strom et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 8,095
- views
-
- 1,030
- downloads
-
- 99
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
HP1α is a chromatin crosslinker that controls nuclear and mitotic chromosome mechanics
eLife 10:e63972.
https://doi.org/10.7554/eLife.63972
Further reading
-
- Cell Biology
Understanding the unique susceptibility of the human kidney to pH dysfunction and injury in cystinosis is paramount to developing new therapies to preserve renal function. Renal proximal tubular epithelial cells (RPTECs) and fibroblasts isolated from patients with cystinosis were transcriptionally profiled. Lysosomal fractionation, immunoblotting, confocal microscopy, intracellular pH, TEM, and mitochondrial stress test were performed for validation. CRISPR, CTNS -/- RPTECs were generated. Alterations in cell stress, pH, autophagic turnover, and mitochondrial energetics highlighted key changes in the V-ATPases in patient-derived and CTNS-/- RPTECs. ATP6V0A1 was significantly downregulated in cystinosis and highly co-regulated with loss of CTNS. Correction of ATP6V0A1 rescued cell stress and mitochondrial function. Treatment of CTNS -/- RPTECs with antioxidants ATX induced ATP6V0A1 expression and improved autophagosome turnover and mitochondrial integrity. Our exploratory transcriptional and in vitro cellular and functional studies confirm that loss of Cystinosin in RPTECs, results in a reduction in ATP6V0A1 expression, with changes in intracellular pH, mitochondrial integrity, mitochondrial function, and autophagosome-lysosome clearance. The novel findings are ATP6V0A1’s role in cystinosis-associated renal pathology and among other antioxidants, ATX specifically upregulated ATP6V0A1, improved autophagosome turnover or reduced autophagy and mitochondrial integrity. This is a pilot study highlighting a novel mechanism of tubular injury in cystinosis.
-
- Cell Biology
- Developmental Biology
The rete ovarii (RO) is an appendage of the ovary that has been given little attention. Although the RO appears in drawings of the ovary in early versions of Gray’s Anatomy, it disappeared from recent textbooks, and is often dismissed as a functionless vestige in the adult ovary. Using PAX8 immunostaining and confocal microscopy, we characterized the fetal development of the RO in the context of the mouse ovary. The RO consists of three distinct regions that persist in adult life, the intraovarian rete (IOR), the extraovarian rete (EOR), and the connecting rete (CR). While the cells of the IOR appear to form solid cords within the ovary, the EOR rapidly develops into a convoluted tubular epithelium ending in a distal dilated tip. Cells of the EOR are ciliated and exhibit cellular trafficking capabilities. The CR, connecting the EOR to the IOR, gradually acquires tubular epithelial characteristics by birth. Using microinjections into the distal dilated tip of the EOR, we found that luminal contents flow toward the ovary. Mass spectrometry revealed that the EOR lumen contains secreted proteins potentially important for ovarian function. We show that the cells of the EOR are closely associated with vasculature and macrophages, and are contacted by neuronal projections, consistent with a role as a sensory appendage of the ovary. The direct proximity of the RO to the ovary and its integration with the extraovarian landscape suggest that it plays an important role in ovary development and homeostasis.
