Expression of the gene encoded by a family of macronuclear chromosomes generated by alternative DNA processing inOxytricha fallax

Abstract

ABSTRACT

Two two-gene macronuclear chromosomes of the hypotrichous ciliatesOxytricha fallax andO. trifallax generated by alternative processing of the 81 locus

“…The left-arm introns are rich in A 1 T nucleotides (79.5%) in comparison with the four exons (64.9% A 1 T), as is typical for ciliate introns [Csank et al, 1990;Hoffman et al, 1995], and have donor, acceptor, and putative branch point sequences that match consensus sequences conserved between the introns of alleles of the CR-MSC gene (see Fig. 3; [Williams and Herrick, 1991;Seegmiller et al, 1996]). The left-arm introns have diverged more than the exons: Exons have diverged 3.6% (vA from vC), 6.7% (vA from 310), and 7.3% (vC from 310), whereas the introns have diverged 9.3% (vA/vC), 19.0% (vA/310), and 22.5% (vC/310).…”

“…Figure 4B shows diagonalization analysis comparing its protein sequence with that of DIF-1, a recognized MSC family member [Runs- [Williams and Herrick, 1991;Seegmiller et al, 1996]. Matches between the intron nucleotides and consensi are underlined; nonmatching nucleotides are in lower case.…”

“…For example, in O. fallax, only UGA encodes translation termination, while UAA and UAG encode glutamine [Williams and Herrick, 1991]. Analysis of codon usage patterns of the leftand right-arm genes shows that 62% (110) of the 176 glutamine codons of the right-arm gene and 71% (10) …”

A proposed superfamily of transposase genes: transposon-like elements in ciliated protozoa and a common "D35E" motif.

“…Inserts of nested sets of unidirectional deletion clones were constructed and sequenced as described (13) (3.8). pogo has often cropped up in our database searches, but alignments with IS630-Tcl family members are not sufficiently impressive to present.…”

Recent Evidence for Evolution of the Genetic Code

“…However, to establish the assignment of UAR codons in Oxytricha/Stylonichia, further investigations, such as identification of the responsible tRNA, are required. Quite recently, UAA and, probably, UAG were reported to code for Gln in Oxytricha fallax (241). Interestingly, two Acetabularia species (unicellular green algae which are far from ciliates phylogenetically) also use UAR for Gln codons (205 (139).…”