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Nucleolar dominance: A 'David and Goliath' chromatin imprint process
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Autores
Orientador(es)
Resumo(s)
Nucleolar dominance is an enigma. The puzzle of differential amphiplasty has remained unresolved since it
was first recognised and described in Crepis hybrids by Navashin in 1934. Here we review the body of knowledge that
has grown out of the many models that have tried to find the genetic basis for differential rRNA gene expression in
hybrids, and present a new interpretation. We propose and discuss a chromatin imprinting model which re-interprets
differential amphiplasty in terms of two genomes of differing size occupying a common space within the nucleus, and with
heterochromatin as a key player in the scenario. Difference in size between two parental genomes induces an inherited
epigenetic mark in the hybrid that allows patterns of chromatin organization to have positional effects on the neighbouring
domains. This chromatin imprinting model can be also used to explain complex genomic interactions which transcend
nucleolar dominance and which can account for the overall characteristics of hybrids. Gene expression in hybrids, relative
to parentage, is seen as being based on the nuclear location of the sequences concerned within their genomic environment,
and where the presence of particular repetitive DNA sequences are ‘sensed’, and render silent the adjacent information.
Descrição
Palavras-chave
chromatin imprinting nucleus genome hybrid nucleolar dominance
Contexto Educativo
Citação
"Current Genomics". ISSN 1389-2029. 3 (2002) 563-576