Chris W. Lehman

TBX3 regulates splicing in vivo: a novel molecular mechanism for Ulnar-mammary syndrome.

TBX3 is a member of the T-box family of transcription factors with critical roles in development, oncogenesis, cell fate, and tissue homeostasis. TBX3 mutations in humans cause complex congenital malformations and Ulnar-mammary syndrome. Previous investigations into TBX3 function focused on its activity as a transcriptional repressor. We used an unbiased proteomic approach to identify TBX3 interacting proteins in vivo and discovered that TBX3 interacts with multiple mRNA splicing factors and RNA metabolic proteins. We discovered that TBX3 regulates alternative splicing in vivo and can promote or inhibit splicing depending on context and transcript. TBX3 associates with alternatively spliced mRNAs and binds RNA directly. TBX3 binds RNAs containing TBX binding motifs, and these motifs are required for regulation of splicing. Our study reveals that TBX3 mutations seen in humans with UMS disrupt its splicing regulatory function. The pleiotropic effects of TBX3 mutations in humans and mice likely result from disrupting at least two molecular functions of this protein: transcriptional regulation and pre-mRNA splicing.

Chapter 24 DNA Recombination and Repair in Oocytes Eggs, and Extracts

Publisher Summary This chapter describes successful approaches to investigation recombination in oocytes and/or eggs and the repair of mismatches, and lesions induced by ultraviolet (UV) and X irradiation. Xenopus oocytes store large quantities of materials for use in the early stages of embryogenesis. In the first several hours after fertilization, a major metabolic activity of cleavage stage embryos is DNA synthesis. It has been, therefore, no great surprise to find that enzymes involved in DNA metabolism are abundant in oocytes and eggs. In the cases of some of the enzymes, activities are masked or suppressed in oocytes, as oocytes are not capable of replicative DNA synthesis. In addition to replication, two other processes are usually included in the three Rs of DNA metabolism: recombination and repair. For purposes of this chapter, it is useful to distinguish two styles of recombination. Homologous recombination depends on extensive sequence similarity between interacting chromosomes, whereas homology-independent (or illegitimate) recombination leads to the joining of unrelated sequences, frequently by ligating molecular ends. DNA repair is a collective term for processes that deal with DNA damage of many different kinds.