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Title: Changing Transcriptional Initiation Sites and Alternative 5'- and 3'-Splice Site Selection of the First Intron Deploys the Arabidopsis Protein Isoaspartyl Methyltransferase2 Variants to Different Subcellular Compartments

Author
item Dinkins, Randy
item MAJEE, SUSMITA - UNIV OF KY HORTICULTURE
item NAYAK, NIHAR - UNIV OF KY PLANT SCIENCE
item MARTIN, DAVID - UNIV OF KY HORTICULTURE
item XU, QILONG - LOUISIANA STATE UNIVERSIT
item BELCASTRO, MARISA - UNIVERSITY OF KENTUCKY
item HOUTZ, ROBERT - UNIV OF KY HORTICULTURE
item BEACH, CAROL - UNIV OF KY HORTICULTURE
item DOWNIE, A. BRUCE - UNIV OF KY HORTICULTURE

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2008
Publication Date: 5/1/2008
Citation: Dinkins, R.D., Majee, S.M., Nayak, N.R., Martin, D., Xu, Q., Belcastro, M.P., Houtz, R., Beach, C.M., Downie, A. 2008. Changing Transcriptional Initiation Sites and Alternative 5'- and 3'-Splice Site Selection of the First Intron Deploys the Arabidopsis Protein Isoaspartyl Methyltransferase2 Variants to Different Subcellular Compartments. Plant Journal. doi:10.1111/j.1365-313X.2008.03471.x

Interpretive Summary: Arabidopsis thaliana (L.) Heynh. possesses two PROTEIN-L-ISOASPARTATE METHYLTRANSFERASE (PIMT), genes encoding an enzyme capable of repairing, L-isoaspartyl residues, that arise spontaneously in proteins. The PIMT2 produces at least eight transcripts by using four transcriptional initiation sites that contain three different start codons, and 5'- and 3'-alternative splice site selection of the first intron. The transcripts produced proteins capable of converting L-isoaspartate to L-aspartate in small peptide substrates and of rescuing enzymatic activity of damaged GUS in vitro. PIMT:GFP fusion proteins generated detectable signal in the nucleus. However, whether the protein was also detectable in the cytoplasm, endo-membrane system, chloroplasts, and/or mitochondria, depended on the transcript from which it was produced. The implications of using transcriptional mechanisms to expand a single gene's repertoire to protein variants capable of entry into the various subcellular compartments are discussed in light of PIMT’s presumed role repairing damaged proteins.

Technical Abstract: Arabidopsis thaliana (L.) Heynh. possesses two PROTEIN-L-ISOASPARTATE METHYLTRANSFERASE (PIMT), genes encoding an enzyme (EC 2.1.1.77) capable of converting uncoded, L-isoaspartyl residues, arising spontaneously at L-asparaginyl and L-aspartyl sites in proteins, to L-aspartate. PIMT2 produces at least eight transcripts by using four transcriptional initiation sites (TIS; resulting in three different initiating methionines) and both 5'- and 3'-alternative splice site selection of the first intron. The transcripts produced proteins capable of converting L-isoaspartate to L-aspartate in small peptide substrates and of rescuing enzymatic activity of damaged GUS in vitro. PIMT:GFP fusion proteins generated detectable signal in the nucleus. However, whether the protein was also detectable in the cytoplasm, endo-membrane system, chloroplasts, and/or mitochondria, depended on the transcript from which it was produced. The implications of using transcriptional mechanisms to expand a single gene's repertoire to protein variants capable of entry into the cell's various compartments are discussed in light of PIMT’s presumed role repairing the proteome.