Donald Hucks

Graduation Semester and Year

2008

Language

English

Document Type

Thesis

Degree Name

Master of Science in Biology

Department

Biology

First Advisor

Cedric Feschotte

Abstract

A growing body of work suggests that the exaptation of transposon-derived sequences to perform beneficial cellular functions has played a significant role in eukaryotic evolution. In chapter 1, we present an analysis of 10 exapted pogo transposons in the human genome. We present evidence that all 10 are restricted to tetrapods, and that 8 of the 10 arose early in mammalian evolution, in several independent exaptation events involving diverse pogo lineages. We show that all 10 have been subject to stringent selection throughout mammalian evolution, with pseudogenization having occurred only infrequently. In 4 of these genes, we observed no cases of gene loss, consistent with a very high selective value for these genes. We also present evidence that all 10 genes encode sequence-specific DNA-binding proteins, each likely to bind a highly constrained, but as yet unknown, sequence somewhere within the mammalian genome. In chapter 2, we present evidence that a motif occurring within the terminal inverted repeats (TIRs) of Hsmar1 and made1 transposons is subject to purifying selection at a number of loci in anthropoid genomes as binding sites for SETMAR, the protein product of an anthropoid-specific gene formed some 50 mya by fusion of an Hsmar1 transposon with an extant histone methyltransferase gene. Together, our analyses support the notion that this complementary nature of transposon exaptation, the host recruitment of transposase as DNA-binding protein and non-coding transposon sequence as binding site, has been a recurrent theme in mammalian evolution.

Disciplines

Biology | Life Sciences

Comments

Degree granted by The University of Texas at Arlington

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