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The Drosophila mitochondrial translation elongation factor G1 contains a nuclear localization signal and inhibits growth and DPP signaling.

Trivigno C, Haerry TE - PLoS ONE (2011)

Bottom Line: Expression of missense mutant forms of EF-G1 can accumulate in the nucleus and cause growth and patterning defects and animal lethality.We find that transgenes that encode mutant human EF-G1 proteins can rescue ico mutants, indicating that the underlying problem of the human disease is not just the loss of enzymatic activity.Our results are consistent with a model where EF-G1 acts as a retrograde signal from mitochondria to the nucleus to slow down cell proliferation if mitochondrial energy output is low.

View Article: PubMed Central - PubMed

Affiliation: Center for Molecular Biology and Biotechnology, Florida Atlantic University, Boca Raton, Florida, United States of America.

ABSTRACT
Mutations in the human mitochondrial elongation factor G1 (EF-G1) are recessive lethal and cause death shortly after birth. We have isolated mutations in iconoclast (ico), which encodes the highly conserved Drosophila orthologue of EF-G1. We find that EF-G1 is essential during fly development, but its function is not required in every tissue. In contrast to mutations, missense mutations exhibit stronger, possibly neomorphic phenotypes that lead to premature death during embryogenesis. Our experiments show that EF-G1 contains a secondary C-terminal nuclear localization signal. Expression of missense mutant forms of EF-G1 can accumulate in the nucleus and cause growth and patterning defects and animal lethality. We find that transgenes that encode mutant human EF-G1 proteins can rescue ico mutants, indicating that the underlying problem of the human disease is not just the loss of enzymatic activity. Our results are consistent with a model where EF-G1 acts as a retrograde signal from mitochondria to the nucleus to slow down cell proliferation if mitochondrial energy output is low.

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Sequence alignment of Drosophila and human EF-G1 and EF-G2 proteins.Sequence alignment of the Drosophila and human EF-G1 and EF-G2 proteins (dEF-G1, hEF-G1, dEF-G2, hEF-G2). The positions of the identified fly and human EF-G1 mutations shown in Figure 3 are indicated by numbers (1–11) [4], [5], [6].
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pone-0016799-g002: Sequence alignment of Drosophila and human EF-G1 and EF-G2 proteins.Sequence alignment of the Drosophila and human EF-G1 and EF-G2 proteins (dEF-G1, hEF-G1, dEF-G2, hEF-G2). The positions of the identified fly and human EF-G1 mutations shown in Figure 3 are indicated by numbers (1–11) [4], [5], [6].

Mentions: Complementation tests with well-defined deficiencies on L2 indicated that the mutations might be located within CG4567, which encodes the Drosophila orthologue of the mitochondrial elongation factor G1 (dEF-G1; Figure 2). To identify the gene, we generated imprecise excisions of various P-elements including EY05983, which is located 3′ of CG4567. We isolated two deletions, icoDel EY1 and icoDel EY2, which failed to complement ico alleles. Subsequent sequencing revealed that the EMS-induced mutations contained single or double missense mutations in various regions of CG4567 (Figures 2 and 3). Both deletions remove the C-terminal RNA binding domains of CG4567 (Figure 3), which according to structural comparison mimic the shape of a tRNA and are used to interact with ribosomes [13]. Thus, the deletion mutations most likely represent mutations, since the resulting truncated proteins are not expected to form functional complexes with ribosomes. Although the allele icoDel EY2 also lacks a portion of the neighboring gene CG13784, the phenotypes of the two deletions are identical. Interestingly, homozygous or transheterozygous animals of the two deletions are not embryonic lethal like the four missense mutations but develop for two additional days to the early third instar larval stage, where they arrest development and die several days later. Animals with a combination of a missense mutation and a deletion die shortly after embryogenesis as malformed first instar larvae. In contrast to missense mutations, the two deletions also do not interact with DPP signaling in both genetic screens. Taken together, our results show that ico alleles are mutations in CG4567 and that missense mutations that encode full-length EF-G1 proteins cause a more severe phenotype than mutations.


The Drosophila mitochondrial translation elongation factor G1 contains a nuclear localization signal and inhibits growth and DPP signaling.

Trivigno C, Haerry TE - PLoS ONE (2011)

Sequence alignment of Drosophila and human EF-G1 and EF-G2 proteins.Sequence alignment of the Drosophila and human EF-G1 and EF-G2 proteins (dEF-G1, hEF-G1, dEF-G2, hEF-G2). The positions of the identified fly and human EF-G1 mutations shown in Figure 3 are indicated by numbers (1–11) [4], [5], [6].
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3045377&req=5

pone-0016799-g002: Sequence alignment of Drosophila and human EF-G1 and EF-G2 proteins.Sequence alignment of the Drosophila and human EF-G1 and EF-G2 proteins (dEF-G1, hEF-G1, dEF-G2, hEF-G2). The positions of the identified fly and human EF-G1 mutations shown in Figure 3 are indicated by numbers (1–11) [4], [5], [6].
Mentions: Complementation tests with well-defined deficiencies on L2 indicated that the mutations might be located within CG4567, which encodes the Drosophila orthologue of the mitochondrial elongation factor G1 (dEF-G1; Figure 2). To identify the gene, we generated imprecise excisions of various P-elements including EY05983, which is located 3′ of CG4567. We isolated two deletions, icoDel EY1 and icoDel EY2, which failed to complement ico alleles. Subsequent sequencing revealed that the EMS-induced mutations contained single or double missense mutations in various regions of CG4567 (Figures 2 and 3). Both deletions remove the C-terminal RNA binding domains of CG4567 (Figure 3), which according to structural comparison mimic the shape of a tRNA and are used to interact with ribosomes [13]. Thus, the deletion mutations most likely represent mutations, since the resulting truncated proteins are not expected to form functional complexes with ribosomes. Although the allele icoDel EY2 also lacks a portion of the neighboring gene CG13784, the phenotypes of the two deletions are identical. Interestingly, homozygous or transheterozygous animals of the two deletions are not embryonic lethal like the four missense mutations but develop for two additional days to the early third instar larval stage, where they arrest development and die several days later. Animals with a combination of a missense mutation and a deletion die shortly after embryogenesis as malformed first instar larvae. In contrast to missense mutations, the two deletions also do not interact with DPP signaling in both genetic screens. Taken together, our results show that ico alleles are mutations in CG4567 and that missense mutations that encode full-length EF-G1 proteins cause a more severe phenotype than mutations.

Bottom Line: Expression of missense mutant forms of EF-G1 can accumulate in the nucleus and cause growth and patterning defects and animal lethality.We find that transgenes that encode mutant human EF-G1 proteins can rescue ico mutants, indicating that the underlying problem of the human disease is not just the loss of enzymatic activity.Our results are consistent with a model where EF-G1 acts as a retrograde signal from mitochondria to the nucleus to slow down cell proliferation if mitochondrial energy output is low.

View Article: PubMed Central - PubMed

Affiliation: Center for Molecular Biology and Biotechnology, Florida Atlantic University, Boca Raton, Florida, United States of America.

ABSTRACT
Mutations in the human mitochondrial elongation factor G1 (EF-G1) are recessive lethal and cause death shortly after birth. We have isolated mutations in iconoclast (ico), which encodes the highly conserved Drosophila orthologue of EF-G1. We find that EF-G1 is essential during fly development, but its function is not required in every tissue. In contrast to mutations, missense mutations exhibit stronger, possibly neomorphic phenotypes that lead to premature death during embryogenesis. Our experiments show that EF-G1 contains a secondary C-terminal nuclear localization signal. Expression of missense mutant forms of EF-G1 can accumulate in the nucleus and cause growth and patterning defects and animal lethality. We find that transgenes that encode mutant human EF-G1 proteins can rescue ico mutants, indicating that the underlying problem of the human disease is not just the loss of enzymatic activity. Our results are consistent with a model where EF-G1 acts as a retrograde signal from mitochondria to the nucleus to slow down cell proliferation if mitochondrial energy output is low.

Show MeSH