Changes in the complexity of nuclear RNA during development of Dictyostelium discoideum☆

[摘要] Saturationhybridizationwitharadioactivesingle-copygenomicDNAprobehasbeenusedtomeasurethecomplexityofthetotalwholecellpolyadenylatedRNApopulationsduringdevelopmentofthecellularslimemoldDictyosteliumdiscoideum.ThecomplexityofthepolyadenylatednuclearRNAhasbeendeducedbycomparisonofthesenumberswithourpreviousestimatesofthecomplexityofthepolyadenylatedRNAinthecytoplasmandonpolysomes.Assumingasymmetrictranscription,53to54%ofthesingle-copyportionofthegenomeisexpressedinpolyadenylatedRNAingrowingandearlyaggregatingcells.Ofthisonlyaboutone-thirdor19%isexpressedonpolysomesasmRNA.Bycontrast,duringlateaggregationandculmination,afterthetimewhentipshaveformedontheaggregatesasubstantiallygreaterportionofthesingle-copygenome,80%,isexpressedinthetotalpopulationofpolyadenylatedRNA.Again,however,onlyaboutone-thirdor30%ofthesingle-copygenomeisexpressedasmRNA.ThusthroughoutgrowthanddevelopmentthecomplexityofthepolyadenylatednuclearRNAisaboutoneandone-halftimesthecomplexityofthecorrespondingmRNApopulations.TheRNApopulationfromthelatedevelopingcellsiscomposedofallthoseRNAspeciesexpressedduringgrowthandearlydevelopmentplusadditionalRNAspecieswhoseexpressionisspecifictolatedevelopment.SequenceswhichcomprisethemajorityofthemassofthenewpolyadenylatedRNAtranscriptswhichappearinthecytoplasmandonthepolysomeslateinaggregationarenotdetectableinnuclearRNAfromgrowingcells.Thissuggeststhattheirdevelopmentalexpressionislargelyregulatedattheleveloftranscriptionratherthanbycontrolsatthelevelofprocessingortransportfromthenucleus.

[学科分类] 生物科学（综合）