RESUMEN
In eukaryotes, ribonuclease H1 (RNase H1) is involved in the processing and removal of RNA/DNA hybrids in both nuclear and mitochondrial DNA. The enzyme comprises a C-terminal catalytic domain and an N-terminal hybrid-binding domain (HBD), separated by a linker of variable length, 115 amino acids in Drosophila melanogaster (Dm). Molecular modelling predicted this extended linker to fold into a structure similar to the conserved HBD. Based on a deletion series, both the catalytic domain and the conserved HBD were required for high-affinity binding to heteroduplex substrates, while loss of the novel HBD led to an â¼90% drop in Kcat with a decreased KM, and a large increase in the stability of the RNA/DNA hybrid-enzyme complex, supporting a bipartite-binding model in which the second HBD facilitates processivity. Shotgun proteomics following in vivo cross-linking identified single-stranded DNA-binding proteins from both nuclear and mitochondrial compartments, respectively RpA-70 and mtSSB, as prominent interaction partners of Dm RNase H1. However, we were not able to document direct and stable interactions with mtSSB when the proteins were co-overexpressed in S2 cells, and functional interactions between them in vitro were minor.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/enzimología , Ribonucleasa H/metabolismo , Animales , Dominio Catalítico , Proteínas de Unión al ADN/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Modelos Moleculares , Unión Proteica , Ribonucleasa H/química , Ribonucleasa H/genética , Homología de Secuencia de Aminoácido , Relación Estructura-Actividad , Especificidad por SustratoRESUMEN
Cancer is a multistep process. In the early phases of this disease, mutations in oncogenes and tumor suppressors are thought to promote clonal expansion. These mutations can increase cell competitiveness, allowing tumor cells to grow within the tissue by eliminating wild type host cells. Recent studies have shown that cell competition can also function in later phases of cancer. Here, we examine the existing evidence linking cell competition and tumorigenesis. We focus on the mechanisms underlying cell competition and their contribution to disease pathogenesis.
Asunto(s)
Transformación Celular Neoplásica/patología , Neoplasias/patología , Animales , Comunicación Celular/fisiología , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Progresión de la Enfermedad , Regulación Neoplásica de la Expresión Génica , Humanos , Mutación , Neoplasias/etiología , Neoplasias/genética , Neoplasias/metabolismo , OncogenesRESUMEN
The aminoacylation of tRNAs by aminoacyl-tRNA synthetases (ARSs) is a central reaction in biology. Multiple regulatory pathways use the aminoacylation status of cytosolic tRNAs to monitor and regulate metabolism. The existence of equivalent regulatory networks within the mitochondria is unknown. Here, we describe a functional network that couples protein synthesis to DNA replication in animal mitochondria. We show that a duplication of the gene coding for mitochondrial seryl-tRNA synthetase (SerRS2) generated in arthropods a paralog protein (SLIMP) that forms a heterodimeric complex with a SerRS2 monomer. This seryl-tRNA synthetase variant is essential for protein synthesis and mitochondrial respiration. In addition, SLIMP interacts with the substrate binding domain of the mitochondrial protease LON, thus stimulating proteolysis of the DNA-binding protein TFAM and preventing mitochondrial DNA (mtDNA) accumulation. Thus, mitochondrial translation is directly coupled to mtDNA levels by a network based upon a profound structural modification of an animal ARS.