biostudies-literatureUnknown6Sobhy HGenomic analysis of giant viruses, such as Mimivirus, has revealed that more than half of the putative genes have no known functions (ORFans). We knocked down Mimivirus genes using short interfering RNA as a proof of concept to determine the functions of giant virus ORFans. As fibers are easy to observe, we targeted a gene encoding a protein absent in a Mimivirus mutant devoid of fibers as well as three genes encoding products identified in a protein concentrate of fibers, including one ORFan and one gene of unknown function. We found that knocking down these four genes was associated with depletion or modification of the fibers. Our strategy of silencing ORFan genes in giant viruses opens a way to identify its complete gene repertoire and may clarify the role of these genes, differentiatiFrontiers in microbiology345https://www.ebi.ac.uk/biostudies/studies/S-EPMC4412084biostudies-literatureIdentification of giant Mimivirus protein functions using RNA interference.PMC4412084Scola BLColson PPagnier ISobhy HRaoult DfalseIdentification of giant Mimivirus protein functions using RNA interference.Genomic analysis of giant viruses, such as Mimivirus, has revealed that more than half of the putative genes have no known functions (ORFans). We knocked down Mimivirus genes using short interfering RNA as a proof of concept to determine the functions of giant virus ORFans. As fibers are easy to observe, we targeted a gene encoding a protein absent in a Mimivirus mutant devoid of fibers as well as three genes encoding products identified in a protein concentrate of fibers, including one ORFan and one gene of unknown function. We found that knocking down these four genes was associated with depletion or modification of the fibers. Our strategy of silencing ORFan genes in giant viruses opens a way to identify its complete gene repertoire and may clarify the role of these genes, differentiati2015-01-01T00:00:00Z20152025-04-04T23:23:59.478Z2019-03-27T01:50:38ZS-EPMC44120842597284610.3389/fmicb.2015.00345