Research Projects
One of the essential capabilities of all living organisms is their ability to reproduce themselves given favorable conditions. This vital process necessitates the coordination of many complex biochemical pathways, including sensing and responding to environmental conditions, as well as undertaking the substantial biosynthetic commitments essential to duplicating the cellular constituents. Central to this process is the regulation of the biosynthesis of ribosomes – those organelles that cells use to produce new proteins. To make a ribosome, cells must produce and assemble some 79 individual proteins, as well as 4 highly modified and processed rRNAs. In total, ribosome production depends on the activity of several hundred gene products, and in yeast cells, it represents the major metabolic commitment of the total cellular economy.
Our research over the past several years has shown that there are some 200 hundred transcriptionally coregulated genes in yeast (called the RRB regulon) that play a role in rRNA and ribosome biosynthesis. This observation makes sense in that it would be advantageous for yeast cells to regulate the expression of this large set of functionally related genes as a group. When demand for ribosome production is high (i.e. during cell division), they would all be turned on; when new ribosome demand is low, they would be turned off. One, as yet unanswered question, is how this large set of genes is turned on and off.
Through bioinformatics approaches, we have found that the members of the RRB regulon are highly enriched for two promoter motifs (known as PAC and RRPE). Since these short consensus sequences are ideally positioned upstream of the majority of the RRB genes, we are testing the hypothesis that they are important for regulating RRB gene expression levels in response to changing cellular conditions. We are currently taking a genetic approach to define the roles that RRPE and PAC play in modulating RRB gene expression, both when situated upstream of single or pairs of RRB genes (Fig. 1). We are also interested in identifying the factors that bind to the PAC and RRPE motifs, and to characterize how their activities may contribute to altered RRB gene expression levels in response to varying cellular conditions (i.e. heat shock, osmotic shock etc.).
Selected References
C. Wade, M.A. Umbarger, and M.A. McAlear 2006 The yeast rRNA and ribosome biosynthesis (RRB) regulon contains over 200 genes. Yeast 23:293-306.
C. Ionescu, S. Origanti and M. McAlear 2004 The yeast rRNA biosynthesis factor Ebp2p is also required for efficient nuclear division. Yeast 21:1219-1232
L. Green, M. Schotanus, M. A. McAlear and E. A. Howell 2003 Atomic force microscopy can detect the binding of yeast Replication Factor C to DNA Nano Letters 3:39-41.
C. Ionescu, K. Shea, R. Mehra, L. Prundeanu and M. A. McAlear 2002 Monomeric yeast PCNA mutants are defective in interacting with, and stimulating the ATPase activity of RFC. Biochemistry 41:12975-85.
M. Lei, I.H. Cheng, L. A. Roberts, M. A. McAlear, and B. K. Tye 2002 Two mcm3 mutants affect different steps in the initiation of DNA replication. J. Biol. Chem. 277:30824-30831.
C. Wade, K. Shea, R.V. Jensen and M. McAlear 2001 EBP2 is a member of the yeast RRB regulon, a transcriptionaly co-regulated set of genes that are required for ribosome and rRNA biosynthesis Mol. Cell. Bio. 21:8638-8650.
W. Beckwith and M. A. McAlear 2000 Allele-specific interactions between the yeast RFC1 and RFC5 genes suggest a basis for RFC subunit-subunit interactions. Mol. Gen. Genetics 264:378-391.
Michael D. Huber, Jessica H. Dworet, Kathy Shire, Lori Frappier and Michael A. McAlear
2000 The budding yeast homolog of the human EBNA1-binding-protein 2 (Ebp2p) is an essential nucleolar protein required for pre-rRNA processing. J. Biol. Chem. 275: 28764-28773.
Principle Investigator
Mike McAlear
