The paracentric inversion In(2Rh)PL alters the centromeric organization of chromosome 2 in Drosophila melanogaster

Centromeres are complex structures involved in an evolutionarily conserved function, the correct segregation of chromosomes and chromatids during meiosis and mitosis. The centromere is determined by epigenetic processes that result in a particular nucleosome organization (CEN chromatin) that differs from the rest of the chromatin including the heterochromatin that normally surrounds the centromere in higher organisms. Many of the current models of centromere origin and organization rely on the molecular and cytological characterization of minichromosomes and their derivatives, and on studies on the origin and maintenance of neocentromeres. Here, we describe the peculiar centromere organization observed in In(2Rh)PL, a paracentric D. melanogaster inversion in which the centromere is maintained in its natural context but is directly flanked by a euchromatic domain as a result of the rearrangement. We have identified the breakpoints of the inversion and show that the proximal one is within the centromere region. The data presented suggest that, notwithstanding the loss of all the pericentric 2Rh heterochromatin, the centromere of the In(2Rh)PL chromosome is still active but presents a nucleosomal organization quite different from the organization usually observed in the centromeric region

Epigenetic mechanisms regulating COVID-19 infection

Coronavirus disease 2019 (COVID-2019) outbreak originating in December 2019 in Wuhan, China has emerged as a global threat to human health. The highly contagious SARS-CoV-2 infection and transmission presents a diversity of human host and increased disease risk with advancing age, highlighting the importance of in-depth understanding of its biological properties. Structural analyses have elucidated hot spots in viral binding domains, mutations, and specific proteins in the host such as the receptor angiotensin-converting enzyme 2 (ACE2) and the transmembrane protease serine 2 (TMPRSS2) to be implicated in cell entry and viral infectivity. Furthermore, epigenetic changes that regulate chromatin structure have shown a major impact in genome stabilization and maintenance of cellular homoeostasis and they have been implicated in the pathophysiology of the virus infection. Epigenetic research has revealed that global DNA methylation along with ACE2 gene methylation and post-translational histone modifications may drive differences in host tissue-, biological age- and sex-biased patterns of viral infection. Moreover, modulation of the host cells epigenetic landscape following infection represents a molecular tool used by viruses to antagonize cellular signalling as well as sensing components that regulate the induction of the host innate immune and antiviral defence programmes in order to enhance viral replication and infection efficiency. In this review, we provide an update of the main research findings at the interface of epigenetics and coronavirus infection. In particular, we highlight the epigenetic factors that interfere with viral replication and infection and may contribute to COVID-19 susceptibility, offering new ways of thinking in respect to host viral response

Drosophila dosage compensation: Males are from Mars, females are from Venus

Dosage compensation of X-linked genes is a phenomenon of concerted, chromosome-wide regulation of gene expression underpinned by sustained and tightly regulated histone modifications and chromatin remodeling, coupled with constrains of nuclear architecture. This elaborate process allows the accomplishment of regulated expression of genes on the single male X chromosome to levels comparable to those expressed from the two X chromosomes in females. The ribonucleoprotein Male Specific Lethal (MSL) complex is enriched on the male X chromosome and is intricately involved in this process in Drosophila melanogaster. In this review we discuss the recent advances that highlight the complexity lying behind regulation of gene expression by just 2-fold