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Changing transcriptional initiation sites and alternative 5′‐ and 3′‐splice site selection of the first intron deploys Arabidopsis PROTEIN ISOASPARTYL METHYLTRANSFERASE2 variants to different subcellular compartments
Author(s) -
Dinkins Randy D.,
Majee Susmita Maitra,
Nayak Nihar R.,
Martin David,
Xu Qilong,
Belcastro Marisa P.,
Houtz Robert L.,
Beach Carol M.,
Downie A. Bruce
Publication year - 2008
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2008.03471.x
Subject(s) - intron , arabidopsis , biology , arabidopsis thaliana , gene , alternative splicing , cytoplasm , rna splicing , splice , proteome , microbiology and biotechnology , biochemistry , genetics , exon , rna , mutant
Summary Arabidopsis thaliana (L.) Heynh. possesses two PROTEIN‐L‐ISOASPARTATE METHYLTRANSFERASE ( PIMT ) genes encoding enzymes (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 produce mature proteins capable of converting l ‐isoaspartate to l ‐aspartate in small peptide substrates. PIMT:GFP fusion proteins generated a 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. On‐blot‐methylation of proteins, prior to the completion of germination, indicated that cruciferin subunits contain isoaspartate. 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 in repairing the proteome.