Role of Nonhistone Chromosomal Proteins in Selective Gene Expression
Gerald M. Kolodny in Eukaryotic Gene Regulation, 2018
Adolph and co-workers have investigated the possible role of nonhistone proteins in chromosome structure by dissecting the structural contributions of histones and nonhistone proteins.286 By competition with dextran sulfate and heparin, all the histones and many nonhistone proteins were gently removed from HeLa metaphase chromosomes. The histone-depleted chromosomes had a DNA to protein ratio of 6:1. The protein component consisted of 6 major and 25 minor nonhistone proteins which were all resistant to removal by 2 MNaCl and 0.2 NH2SO4.286 Electron microscopic analysis of these histone-depleted chromosomes showed that they retained the characteristic shape of metaphase chromosomes and consisted of a central structure or “scaffold” surrounded by loops of DNA which were attached to adjacent points on the scaffold.287 When DNA was removed from chromosomes by micrococcal nuclease prior to histone depletion, the nonhistone protein scaffold could still be isolated. It retained the general shape and size of intact chromosomes.288 This result rules out the possibility that the scaffold structure is an artifactual product caused by the rearrangement or trapping of nonhistone proteins during the removal of histones. These experiments demonstrate that by providing a scaffold to which loops of DNA are attached, the nonhistone proteins play an important role in defining the basic shape of chromosomes. It has been proposed that the long DNA loops are condensed by histones into shorter, possibly twisted loops which are arranged around the scaffold.289 Similar scaffold structures have also been isolated from histone-depleted chicken erythroid interphase chromosomes.286
The laboratory basis of medical genetics
Peter S. Harper in The Evolution of Medical Genetics, 2019
The new techniques also allowed much smaller changes in chromosome structure to be recognised, so that a series of new chromosomal malformation syndromes could be defined when combined with careful clinical assessment. This work, much of which resulted from studies in the Paris laboratories of Lejeune and de Grouchy, was brought together in the classical book of de Grouchy and Turleau (1977), Clinical Atlas of Human Chromosomes (see the interview with Catherine Turleau [42]). It also became an important part of the development of the field of clinical dysmorphology, as described in Chapter 4.
Preimplantation Genetic Testing for Structural Rearrangements
Carlos Simón, Carmen Rubio in Handbook of Genetic Diagnostic Technologies in Reproductive Medicine, 2022
Cytogenetics is the study of chromosome structure and properties that capitalizes on the constant morphology and size of normal chromosomes to detect abnormalities [9]. Karyotyping is a useful cytogenetic tool that uses in vitro culture and banding techniques to perform structural and numerical chromosomal analyses in metaphases to describe normal or abnormal chromosome complement of an individual, tissue, or cell line [10]. Currently, karyotyping of peripheral blood samples remains the first-line method for detecting chromosomal abnormalities in infertile couples.
The effect of ionomycin-induced oocyte activation on multiple morphological abnormalities of the sperm flagella
Published in Systems Biology in Reproductive Medicine, 2023
Zhiren Liu, Yujia Guo, Xingting Chen, Chen Lin, Xinxin Guo, Mingting Jiang, Qicai Liu
Day 6 embryos with blastulation failure are suitable for the comparison. Through the transcriptome analysis of day 6 embryos, GO analysis showed that AOA had effects on the terms of ‘protein-DNA complex’, ‘nucleosome’, and ‘DNA packaging complex’. It indicated that AOA had an effect on the chromosome structure of the day 6 embryo. The change in chromosome structure can further affect transcriptional regulation and selective expression of genes. Cell differentiation depends on gene-specific expression. Therefore, cell differentiation may also be affected by AOA. It may be why the blastocysts of AOA groups had more differentiation failure cells. In addition, in the ‘protein heterodimerization activity’ term, except for the genes involved in chromosome structure, most of the rest of the genes are involved in transcriptional regulation. These genes included USF1, NFYB, METTL3, LSM6, GTF2A1, FMR1, CREB3L3, CEBPB, and BHLHE40 (Table 2 and Supplementary Table 3). METTL3 has been shown to be involved in the differentiation of embryonic stem cells (Geula et al. 2015). Therefore, AOA also has a direct effect on transcriptional regulation.
Heterochromatin extension: a possible cytogenetic fate of primary amenorrhea along with normal karyotype
Published in Journal of Obstetrics and Gynaecology, 2022
Bishal Kumar Dey, Shanoli Ghosh, Ajanta Halder, Somajita Chakraborty, Sanchita Roy
The region of heterochromatin also acts as a key part in chromosome structure, histone modification and gene regulation. There is evidence from where we come to know that there may be displacement of heterochromatin from one chromosome to another. Perhaps, this displacement is helping in the extension of a particular chromosome at the heterochromatin portion of the long arm (Bannister and Kouzarides 2011). The mechanisms of spindle fibres, chromosome movement, meiosis crossover and change of sister chromatids are considered to be the integral region as heterochromatin for a chromosome. At the time of meiosis, there may be a change in area of synapses of homologous chromosomes in the polymorphic heterochromatin region. The heterochromatin in chromosomal polymorphism can also regulate gene expression by reversible transformation between heterochromatin (non-coding DNA sequences) and euchromatin (expressed DNA sequences) thus justifying certain clinical expression like short stature or PA. It was also postulated that defective histone protein methylation due to presence of heteromorphic variants may play a more crucial role in ovarian failure. Association of heterochromatin polymorphism with ovarian dysgenesis may be a reason for the occurrence of PA. For that, we need to study on a greater number of patients on the basis of their nucleosome’s functionality and heteromorphic polymorphism by sequencing.
Effects of dam and seqA genes on biofilm and pellicle formation in Salmonella
Published in Pathogens and Global Health, 2018
Sinem Uğur, Nefise Akçelik, Fatma Neslihan Yüksel, Neslihan Taşkale Karatuğ, Mustafa Akçelik
The Dam adenine methyltransferase enzyme encoded by the dam gene recognizes the GATC sequences on the double-stranded DNA and is methylated at position N6. This hemimethylated state of the newly synthesized DNA: allows time for the repair of incorrectly matched bases, the regulation of gene expression, the suppression of the onset of chromosomal replication, and the activation or suppression of cell cycle-related processes [36]. The SeqA protein requires at least two hemimethylated GATC sequences on the same side of the DNA to demonstrate high binding activity. Here it is determined that the SeqA protein function as a nucleoid organizing protein [36]. Proteins involved in the formation and maintenance of chromosome structure, such as SeqA protein, are known to function as global regulators [37].
Related Knowledge Centers
- Adenine
- DNA
- Eukaryote
- Prokaryote
- Cell Nucleus
- Meiosis
- Mitosis
- Chromosome
- Metaphase
- Molecular Structure of Nucleic Acids: A Structure For Deoxyribose Nucleic Acid