Enriched G-quadruplexes on the Drosophila Male X Chromosome Function as Insulators of Dosage Compensation Complex

Abstract

The evolution of sex chromosomes has resulted in half X chromosome dosage in males as females. Dosage compensation, or the two-fold upregulation in males, was thus evolved to balance the gene expression between sexes. However, the step-wise evolutionary trajectory of dosage compensation during Y chromosome degeneration is still unclear. Here, we show that the specific structured elements G-quadruplexes (G4s) are enriched on the X chromosome in Drosophila melanogaster.Meanwhile, on the X chromosome, the G4s are underrepresented on the H4K16 acetylated regions and the binding sites of dosage compensation complex male-specific lethal (MSL) complex. Peaks of G4 density and potential are observed at the flanking regions of MSL binding sites, suggesting G4s act as insulators to precisely up-regulate certain regions in males. Thus, G4s may be involved in the evolution of dosage compensation process through fine-tuning one-dose proto-X chromosome regions around MSL binding sites during the gradual Y chromosome degeneration.

The role of asymptomatic and pre-symptomatic infection in SARS-CoV-2 transmission—a living systematic review

“…Sixteen papers reported either outbreak investigations or contact tracing studies reporting transmission from an index case during the pre-symptomatic period [ 13 , 19 , 21 , 26 , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] ] ( Table 2 ). Of those, eleven studies were included in the quantitative analysis.…”

“…In these studies, having meals together, or playing cards with the index case were exposure activities associated with transmission. The remaining one study reported an outbreak in a restaurant [ 40 ] and four studies exclusively reported family cluster outbreaks [ 30 , 32 , 33 , 39 ]; these investigations did not test contacts outside the household, and it is challenging to truly differentiate transmission during the pre-symptomatic period from symptomatic transmission in the household setting ( Supplementary Figure 1 ).…”