The boundary of macaque rDNA is constituted by low-copy sequences conserved during evolution

Area of Science:

• Genomics
• Evolutionary Biology
• Molecular Genetics

Background:

• Ribosomal DNA (rDNA) arrays are crucial for cell function and are organized in specific chromosomal regions.
• The flanking sequences of rDNA arrays can provide insights into genome evolution and chromosome structure.
• Previous studies have characterized rDNA organization in various species, but comparative analyses of flanking regions are ongoing.

Purpose of the Study:

• To investigate the sequence organization flanking the rDNA array in Macaca mulatta (macaque).
• To compare the rDNA-flanking sequences in macaques with those in other Old World monkeys and apes, including humans.
• To understand the evolutionary dynamics and conservation of these genomic regions.

Main Methods:

• Molecular analysis of DNA sequences from Macaca mulatta, Cercopithecus aethiops, Presbytis cristata, and Hylobates lar.
• Comparative genomics to identify similarities and differences in flanking sequences.
• Analysis of human acrocentric chromosomes to assess evolutionary remodeling.

Main Results:

• The rDNA array in Macaca mulatta is flanked by a composite region containing sequences homologous to human Yp11.2, 4q35.2, and 10p15.3.
• This complex organization appears to be shared among Old World monkeys and lesser apes.
• Evolutionary events led to amplification and spreading of unique DNA regions near rDNA, particularly on the p arm of acrocentric chromosomes.
• Human rDNA boundaries show remodeling, with partial resemblance to macaque 4q35.2 duplications but significant differences in Yp11.2 and absence of 10p15.3 sequences.

Conclusions:

• The sequence organization flanking rDNA arrays in primates, particularly Old World monkeys and lesser apes, exhibits conserved features despite evolutionary modifications.
• The preferential location of these sequences near the nucleolar organizing region (NOR) has been maintained throughout primate evolution.
• Comparative analysis reveals both conserved patterns and species-specific remodeling events in the genomic architecture surrounding rDNA loci.