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Molecular and Cellular Biology, September 1998, p. 5465-5477, Vol. 18, No. 9
Department of Molecular, Cellular, and
Developmental Biology, University of California, Santa Barbara,
California 93106
Received 23 February 1998/Returned for modification 7 April
1998/Accepted 17 June 1998
DNA from the centromere region of linkage group (LG) VII of
Neurospora crassa was cloned previously from a yeast
artificial chromosome library and was found to be atypical of
Neurospora DNA in both composition (AT rich) and complexity
(repetitive). We have determined the DNA sequence of a small portion
(~16.1 kb) of this region and have identified a cluster of three new retrotransposon-like elements as well as degenerate fragments from the
3' end of Tad, a previously identified LINE-like
retrotransposon. This region contains a novel full-length but nonmobile
copia-like element, designated Tcen, that is
only associated with centromere regions. Adjacent DNA contains portions
of a gypsy-like element designated Tgl1. A
third new element, Tgl2, shows similarity to the
Ty3 transposon of Saccharomyces cerevisiae. All
three of these elements appear to be degenerate, containing
predominantly transition mutations suggestive of the repeat-induced
point mutation (RIP) process. Three new simple DNA repeats have also
been identified in the LG VII centromere region. While Tcen
elements map exclusively to centromere regions by restriction fragment
length polymorphism analysis, the defective Tad elements
appear to occur most frequently within centromeres but are also found
at other loci including telomeres. The characteristics and arrangement
of these elements are similar to those seen in the
Drosophila centromere, but the relative abundance of each
class of repeats, as well as the sequence degeneracy of the
transposon-like elements, is unique to Neurospora. These
results suggest that the Neurospora centromere is
heterochromatic and regional in character, more similar to centromeres
of Drosophila than to those of most single-cell yeasts.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Structure of the Chromosome VII Centromere Region
in Neurospora crassa: Degenerate Transposons and
Simple Repeats
*
Corresponding author. Mailing address: Department of
Molecular, Cellular, and Developmental Biology, University of
California, Santa Barbara, CA 93106. Phone: (805) 893-3867. Fax: (805)
893-4724. E-mail: cambarer{at}lifesci.ucsb.edu.
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