Human rDNA Genes: Identification of Four Fractions, Their Functions and Nucleolar Location

Active ribosomal genes, translational homeostasis and oxidative stress in the pathogenesis of schizophrenia and autism

“…The rDNA units, also termed ribosomal repeats (RR), are duplicated many times, with an average copy number of about 400 copies per human diploid genome (Bross and Krone, 1972), forming clusters of various size on the short arms of five pairs of human acrocentric chromosomes (13-15, 21 and 22) acting as nucleolus organizer regions (NOR) of these acrocentrics. Over the past 25 years, we have studied the copy number variation of the RR in human individual genomes (Veiko et al, 1996;Lyapunova et al, 1998) and the phenotypic effects of various copy numbers in health and pathology (Lyapunova et al, 2012). We found reliable evidence to the effect that various individuals have 250 to 670 copies of RR per diploid genome (Veiko et al, 2003), and only portions of the copies, numerically different in different individuals, are transcriptionally active, that is either transcribed or poised for transcription (potentially active or reversibly inactive) (Lyapunova et al, 1998;Lyapunova and Veiko, 2010;Santoro, 2011;Lyapunova et al, 2012).…”

“…Over the past 25 years, we have studied the copy number variation of the RR in human individual genomes (Veiko et al, 1996;Lyapunova et al, 1998) and the phenotypic effects of various copy numbers in health and pathology (Lyapunova et al, 2012). We found reliable evidence to the effect that various individuals have 250 to 670 copies of RR per diploid genome (Veiko et al, 2003), and only portions of the copies, numerically different in different individuals, are transcriptionally active, that is either transcribed or poised for transcription (potentially active or reversibly inactive) (Lyapunova et al, 1998;Lyapunova and Veiko, 2010;Santoro, 2011;Lyapunova et al, 2012). The remaining copies are stably inactive.…”

“…corresponds to 8 1 copies of rDNA (Lyapunova et al, 2012). Consequently, the number of active ribosomal genes, limiting the top level of the cell protein biosynthesis, varies within a range from 120 up to 190 copies, with a mean of ∼ 150 copies in various individual human genomes.…”

“…The summarized size estimation of all the 10 AgNORs ( Fig. 1) can serve as an index of the active ribosomal gene copy number in the individual diploid genome under investigation (Lyapunova et al, 1998(Lyapunova et al, , 2012.…”

“…Any molecular technique developed so far can only count the total number of RR, including both active (potentially active) and stably inactive. The only way to selectively count the active copies is a cytogenetic method based on the staining of metaphase chromosomes with silver nitrate (Lyapunova et al, 2012).…”