Recent observations indicate that the expression of Ure2p occurs in two manners. The predominant form is via cap-dependent initiation of translation. However, under conditions of """"""""stress"""""""", a shorter form of Ure2p is expressed via an IRES that is contained within the coding region of the Ure2 mRNA (corresponding to the Nterminal region of the protein). An apparently unrelated finding has been the identification of the yeast homolog to the human eIF2A gene which is non-essential for yeast growth. However, when the expression of the smaller form of the Ure2p protein (via a reporter system fused to lacZ) was monitored in the eIF2A deletion strain, expression oflacZ was increased 6 to 10-fold. In the simplest of terms, eIF2A would appear to be a suppressor of the IRES function found in the Ure2 mRNA. We propose the following 4 questions to more fully evaluate these findings: 1. What are the cis-acting sequences in Ure2p mRNA that are required to allow internal initiation? 2. What other yeast mRNAs are initiated via internal initiation? 3. How is control of internal initiation regulated, through covalent modification or protein content? 4. What portion of eIF2A is required to suppress internal initiation and with what proteins does it interact in this process? Given the general observation that in many systems, """"""""stress"""""""" leads to cap-independent initiation (i.e. internal initiation), we feel that we have discovered an ideal model system in which to study the switch from capdependent to cap-independent translation. It is anticipated that the mechanism defined in the yeast system will have broad applicability and will likely provide insights into mammalian systems where there have been numerous reports on the utilization of cap-independent translation (heat shock, apoptosis, viral infection, etc.)

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM068079-04
Application #
7162095
Study Section
Physiological Chemistry Study Section (PC)
Program Officer
Tompkins, Laurie
Project Start
2004-01-01
Project End
2008-12-31
Budget Start
2007-01-01
Budget End
2008-12-31
Support Year
4
Fiscal Year
2007
Total Cost
$238,562
Indirect Cost
Name
Case Western Reserve University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
Bentley, Amber A; Merkulov, Sergei M; Peng, Yi et al. (2012) Chimeric glutathione S-transferases containing inserts of kininogen peptides: potential novel protein therapeutics. J Biol Chem 287:22142-50
Reineke, Lucas C; Cao, Yu; Baus, Diane et al. (2011) Insights into the role of yeast eIF2A in IRES-mediated translation. PLoS One 6:e24492
Reineke, Lucas C; Merrick, William C (2009) Characterization of the functional role of nucleotides within the URE2 IRES element and the requirements for eIF2A-mediated repression. RNA 15:2264-77
Reineke, Lucas C; Komar, Anton A; Caprara, Mark G et al. (2008) A small stem loop element directs internal initiation of the URE2 internal ribosome entry site in Saccharomyces cerevisiae. J Biol Chem 283:19011-25
Galkin, Oleksandr; Bentley, Amber A; Gupta, Sujatha et al. (2007) Roles of the negatively charged N-terminal extension of Saccharomyces cerevisiae ribosomal protein S5 revealed by characterization of a yeast strain containing human ribosomal protein S5. RNA 13:2116-28
Hui, Daniel J; Terenzi, Fulvia; Merrick, William C et al. (2005) Mouse p56 blocks a distinct function of eukaryotic initiation factor 3 in translation initiation. J Biol Chem 280:3433-40
Komar, Anton A; Gross, Stephane R; Barth-Baus, Diane et al. (2005) Novel characteristics of the biological properties of the yeast Saccharomyces cerevisiae eukaryotic initiation factor 2A. J Biol Chem 280:15601-11
Komar, Anton A; Hatzoglou, Maria (2005) Internal ribosome entry sites in cellular mRNAs: mystery of their existence. J Biol Chem 280:23425-8
Merrick, William C (2004) Cap-dependent and cap-independent translation in eukaryotic systems. Gene 332:1-11