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#spacer regions

2 public questions tagged with this topic.

Processing of rRNA and tRNA

Internal transcribed spacer is abbreviated as

Within the 45S pre-rRNA, coding regions for mature rRNAs are separated by Internal Transcribed Spacer sequences: ITS1 between 18S and 5.8S, ITS2 between 5.8S and 28S. Unlike NTS, ITS regions are transcribed by Pol I as part of precursor but subsequently excised during maturation by nucleolar processing machineries including RNase MRP and exonucleases like Xrn2 and exosome. Their removal liberates individual rRNAs. Due to rapid evolution and variability, ITS sequences serve as universal DNA barcodes for fungal and plant phylogenetics.

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 8, Internal transcribed spacers ITS1 and ITS2 excision

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Processing of rRNA and tRNA

Non-transcribed spacer is abbreviated as

rDNA is organized as tandem head-to-tail repeats. Between transcription units lies Non-Transcribed Spacer, NTS, historically called intergenic spacer. NTS is not transcribed by RNA Pol I and contains regulatory elements such as promoters, enhancers, terminators, replication origins and chromatin boundary sites controlling rDNA silencing and copy number stability. It contrasts with ETS, external transcribed spacer present at 5' and 3' ends of 45S transcript, and ITS, internal transcribed spacer between mature rRNAs, both initially transcribed then removed during processing. This refined regulat

Ref: NCBI Bookshelf, Molecular Biology of the Cell, Section: Organization of rDNA repeats and NTS

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