Intron conservation in a UV-specific DNA repair gene encoded by chlorella viruses

Large dsDNA-containing chlorella viruses encode a pyrimidine dimer-specific glycosylase (PDG) that initiates repair of UV-induced pyrimidine dimers. The PDG enzyme is a homologue of the bacteriophage T4-encoded endonuclease V. The pdg gene was cloned and sequenced from 42 chlorella viruses isolated...

Full description

Saved in:
Bibliographic Details
Published in:Journal of molecular evolution 2000-01, Vol.50 (1), p.82-92
Main Authors: Sun, L, Li, Y, McCullough, A K, Wood, T G, Lloyd, R S, Adams, B, Gurnon, J R, Van Etten, J L
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Base Sequence
Conserved Sequence
Deoxyribonucleic acid
DNA
DNA Glycosylases
DNA repair
DNA Repair - genetics
DNA Repair - radiation effects
Enzymes
Evolutionary biology
Exons
Genetic Variation
Genetics
Introns
Molecular biology
Molecular Sequence Data
N-Glycosyl Hydrolases - genetics
N-Glycosyl Hydrolases - metabolism
Phycodnaviridae - genetics
Phycodnaviridae - radiation effects
Phylogeny
Ultraviolet Rays
Viruses
Citations: Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Large dsDNA-containing chlorella viruses encode a pyrimidine dimer-specific glycosylase (PDG) that initiates repair of UV-induced pyrimidine dimers. The PDG enzyme is a homologue of the bacteriophage T4-encoded endonuclease V. The pdg gene was cloned and sequenced from 42 chlorella viruses isolated over a 12-year period from diverse geographic regions. Surprisingly, the pdg gene from 15 of these 42 viruses contain a 98-nucleotide intron that is 100% conserved among the viruses and another 4 viruses contain an 81-nucleotide intron, in the same position, that is nearly 100% identical (one virus differed by one base). In contrast, the nucleotides in the pdg coding regions (exons) from the intron-containing viruses are 84 to 100% identical. The introns in the pdg gene have 5'-AG/GTATGT and 3'-TTGCAG/AA splice site sequences which are characteristic of nuclear-located, spliceosomal processed pre-mRNA introns. The 100% identity of the 98-nucleotide intron sequence in the 15 viruses and the near-perfect identity of an 81-nucleotide intron sequence in another 4 viruses imply strong selective pressure to maintain the DNA sequence of the intron when it is in the pdg gene. However, the ability of intron-plus and intron-minus viruses to repair UV-damaged DNA in the dark was nearly identical. These findings contradict the widely accepted dogma that intron sequences are more variable than exon sequences.
ISSN:0022-2844
1432-1432
DOI:10.1007/s002399910009