Mouse mammary adenocarcinoma Ca 755 was studied at two times in its growth: the exponential (8 days) and plateau phase (20 days). Cycling cells were labelled with [3H]thymidine injections at 4-hr intervals over 72-hr periods, i.e. three to five times longer than the generation times for the twentieth day and eighth day tumour cells respectively. By autoradiography, the increase of non-cycling cells in ageing tumours was confirmed. By single cell cytophotometry used after Feulgen staining it has been shown that the cells with a high DNA content (especially a G2-DNA amount) were in a higher proportion in the twentieth day tumours than in their eighth day counterparts. Combined cytophotometric and autoradiographic procedures have shown that nearly all cells with a G2-DNA content entered a non-cycling state in ageing tumours.
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G3 (Bethesda)
October 2024
Molecular, Cellular and Developmental Biology, University of Michigan, 1105 N. University Ave., Ann Arbor, MI 48109, USA.
The mechanisms that maintain a non-cycling status in postmitotic tissues are not well understood. Many cell cycle genes have promoters and enhancers that remain accessible even when cells are terminally differentiated and in a non-cycling state, suggesting their repression must be maintained long term. In contrast, enhancer decommissioning has been observed for rate-limiting cell cycle genes in the Drosophila wing, a tissue where the cells die soon after eclosion, but it has been unclear if this also occurs in other contexts of terminal differentiation.
View Article and Find Full Text PDFmBio
September 2024
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA.
In humans, sterile alpha motif (SAM) domain- and histidine-aspartic acid (HD) domain-containing protein 1 (SAMHD1) is a dNTPase enzyme that prevents HIV-1 infection in non-cycling cells, such as differentiated THP-1 cells and human primary macrophages. Although phosphorylation of threonine 592 (T592) in SAMHD1 is recognized as the primary regulator of the ability to prevent HIV-1 infection, the contributions of SAMHD1 acetylation to this ability remain unknown. Mass spectrometry analysis of SAMHD1 proteins derived from cycling and non-cycling THP-1 cells, primary cycling B cells, and primary macrophages revealed that SAMHD1 is preferentially acetylated at lysine residues 354, 494, and 580 (K354, K494, and K580).
View Article and Find Full Text PDFInt J Mol Sci
June 2024
Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Breast cancer is most common in women, and in most cases there is no evidence of spread and the primary tumor is removed, resulting in a 'cure'. However, in 10% to 30% of these women, distant metastases recur after years to decades. This is due to breast cancer cells disseminating to distant organs and lying quiescent.
View Article and Find Full Text PDFbioRxiv
May 2024
Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor 48109.
The mechanisms that maintain a non-cycling status in postmitotic tissues are not well understood. Many cell cycle genes have promoters and enhancers that remain accessible even when cells are terminally differentiated and in a non-cycling state, suggesting their repression must be maintained long term. In contrast, enhancer decommissioning has been observed for rate-limiting cell cycle genes in the wing, a tissue where the cells die soon after eclosion, but it has been unclear if this also occurs in other contexts of terminal differentiation.
View Article and Find Full Text PDFJ Biol Chem
May 2024
Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois, USA. Electronic address:
Phospholamban (PLB) is a transmembrane micropeptide that regulates the sarcoplasmic reticulum Ca-ATPase (SERCA) in cardiac muscle, but the physical mechanism of this regulation remains poorly understood. PLB reduces the Ca sensitivity of active SERCA, increasing the Ca concentration required for pump cycling. However, PLB does not decrease Ca binding to SERCA when ATP is absent, suggesting PLB does not inhibit SERCA Ca affinity.
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