Fragments of rDNA within the Chinese hamster genome.
We report the isolation and partial characterization of distinct EcoRI fragments of the Chinese hamster genome which contain regions complementary to a 1-kb portion of the mature 18 S ribosomal RNA molecule. This previously undescribed 18 S rDNA-like region, which we have termed a "fragment of ribosomal DNA" (frDNA), has been shown by sequence analysis to correspond to a region extending 1 kb upstream from the 3' terminus of the mature 18 S rRNA. Within the five frDNA-containing clones described here, no other region of the ribosomal RNA cistron was detected, making it unlikely that these are polymorphic forms of the ribosomal DNA repeat. The 18 S rDNA-complementary region appears to be flanked by an imperfect direct repeat, which could have been the result of the retroinsertion of a fragment of ribosomal RNA. Directly adjacent to the 18 S rDNA-like region we have identified nonribosomal sequences which appear common to all of the frDNA-containing clones we examined. At least eight different-sized EcoRI fragments contain frDNAs and the abundance of the frDNAs appears to be of the order of 30 per genome. The occurrence of multiple copies of this ribosomal-nonribosomal chimera suggests that, once formed, the chimera was duplicated within the genome.
Wejksnora
P J
PJ
Department of Biological Sciences, University of Wisconsin, Milwaukee 53201.
Dumenco
V M
VM
Bacsi
S G
SG
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D004262:DNA Restriction Enzymes; D004275:DNA, Ribosomal / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D009710:Nucleotide Mapping; D010957:Plasmids; D012335:RNA, Ribosomal / Q000235:genetics*; D012337:RNA, Ribosomal, 18S / Q000235:genetics*
D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D012337:RNA, Ribosomal, 18S; D004262:DNA Restriction Enzymes