Project:
Genetic Instability Caused by the Environmental Activation of Mobile Elements
Throughout evolution the activity of mobile elements has had a major influence on the shaping of genomes. In humans, mobile elements contribute almost half of the genomic mass. Currently, only the retroelements LINE-1 and the Alu SINE are active. One new L1 or Alu insertion is estimated to occur in every 200 humans born. These insertions in the genome have significantly contributed to genetic disease. The genetic instability caused by the insertional mutagenesis of mobile elements can be a continuing factor in carcinogenesis. Examples include the inactivation of the c-myc gene and the APC tumor suppressor by a mobile element that caused breast cancer and colon cancer in human patients. Thus, retroelements are potent mutagens in the human genome. Previous data demonstrate that SINE expression, and possibly Alu activity, respond to external factors such as heat shock and stress. Therefore, environmental factors could have a major influence in the induction of genetic instability by stimulating the activity of these elements. Despite the mutagenic potential of mobile elements, studies concerning the mechanistic aspects of SINEs and retropsuedogene amplification are in their initial stages. To be able to define the way that the environment modulates the activity of these elements, the retroposition mechanism needs to be resolved.
The project has already been successful in creating a highly efficient SINE retroposition assay which was greatly improved by the generation of a vector supplying an optimized ORF2 from a highly active L1 element. SINE elements depend on L1 components for retroposition, thus the efficiency depends on both L1 components and the SINE vector.
Further goals of the project include determining the role of transcript capping and SRP9/14 in SINE retroposition and evaluating the mechanism by which cadmium and nickel affect retroposition. Appropriate vectors for this research are under construction and a new alternate pol III promoter (H1) that does not require and intact internal A and B box is included in the panel of constructs. Data has also been generated demonstrating that exposure to cadmium and cobalt does not stimulate Alu retroposition in culture the way that it does for L1, indicating that SINEs and LINEs may not use the same mechanism/cellular components for the integration process. Further studies evaluating individual repair proteins (i.e. ERCC-1) on L1 and Alu activity are being evaluated.
Selected Publications:
1- Roy-Engel, A.M., El-Sawy, M., Farooq, L., Odom, G.L., Perepelitsa-Belancio, V., Bruch, H., Oyeniran, O.O., and Deininger, P.L. (2005) Human retroelements may introduce intragenic polyadenylation signals. Cytogenetic and Genome Res. 110:365-371.
2- Kale, S.P., Moore, L., Deininger, P.L., and Roy-Engel, A.M. (2005) Heavy metals stimulate human LINE-1 retrotransposition. Int.J.Env.Res. Public Health. 2: 84-90.
3- El-Sawy, M., Kale, S., Dugan, C., Nguyen, T.Q., Belancio, V., Bruch, H., Roy-Engel, A.M.*, and Deininger, P.L.* (2005) Nickel stimulates L1 retrotransposition through a post-transcriptional mechanism. J. Mol. Biol. J. Mol. Biol. 354: 246-257. *equal senior authors.
4- Kale, S.P., Carmichael M.C., Harris, K., and Roy-Engel, A.M. (2006) Particulated and soluble cadmium increases L1 retrotranspositional activity. Int.J.Env.Res. Public Health. 3: 121-128.
5- Kroutter, E.N.*, Belancio, V.P.*, and Roy- Engel, A.M. (2007) SINEs and LINEs present different amplification dynamics. (in preparation). *equal first authors.
6- Wagstaff, B., Kroutter, E.N., and Roy-Engel, A. M. (2007) Transcriptional capability of the stealth Alu Yb8 loci (in preparation).
7- Wagstaff. B., Kroutter, E.N., and Roy-Engel, A.M. (2007) Regulation of Alu subfamily retroposition through evolution (in progress).
Contact info: aengel@tulane.edu