Avtor/Urednik		Hancock, John M.
Naslov		The contribution of DNA slippage to eukaryotic nuclear 18S rRNA evolution
Tip		članek
Vol. in št.		Letnik 40, št. 6
Leto izdaje		1995
Obseg		str. 629-639
ISSN		0022-2844 - Journal of molecular evolution
Jezik		eng
Abstrakt		Six of 204 eukaryotic nuclear small-subunit ribosomal RNA sequences analyzed show a highly significant degree of clustering of short sequence motifs that indicates the fixation of products of replication slippage within them in their recent evolutionary history. A further 72 sequences show weaker indications of sequence repetition. Repetitive sequences in SSU rRNAs are preferentially located in variable regions and in particular in V4 and V7. The conserved region immediately 5' to V7 (C7) is also consistently repetitive. Whereas variable regions vary in length and appear to have evolved by the fixation of slippage products, C7 shows no indication of length variation. Repetition within C7 is therefore either not a consequence of slippage or reflects very ancient slippage events. The phylogenetic distribution of sequence simplicity in small-subunit rRNAs is patchy, being largely confined to the Mammalia, Apicomplexa, Tetrahymenidae, and Trypanosomatidae. The regions of the molecule associated with sequence simplicity vary with taxonomic grouping as do the sequence motifs undergoing slippage. Comparison of rates of insertion and substitution in a lineage within the genus Plasmodium confirms that both rates are higher in variable regions than in conserved regions. The insertion rate in variable regions is substantially lower than the substitution rate, suggesting that selection acts more strongly on slippage products than on point mutations in these regions. Patterns of coevolution between variable regions may reflect the consequences of selection acting on the incorporation of slippage-derived sequences across the gene.
Proste vsebinske oznake		evkariontsko jedro 18S rRNA evolucija ponovitve zaporedja eukaryotic nuclear 18S rRNA evolution sequence repetition