Noncoding sequences

Splicing is a processing step of the pre-mRNA to become a mature transcript. This involves the excision of intervening noncoding sequences (introns) from coding sequences (exons) by a multiple protein complex, the spliceosome. After splicing the mRNA molecule is ready for translation, since it contains a continuous sequence that encode an entire protein. 

Eukaryotic mRNA synthesis results in a pre-mRNA precursor that contains extensive amounts of excess RNA (introns) that must be precisely removed by RNA splicing to generate functional, translatable mRNA composed of exonic coding and noncoding sequences. 

Figure 39-19. Structure of a typical eukaryotic mRNA showing elements that are involved in regulating mRNA stability. The typical eukaryotic mRNA has a 5 noncoding sequence (5 NCS), a coding region, and a 3 NCS. All are capped at the 5 end, and most have a polyadenylate sequence at the 3 end. The 5 cap and 3 poly(A) tail protect the mRNA against exonuclease attack. Stem-loop structures in the 5 and 3 NCS, features in the coding sequence, and the AU-rich region in the 3 NCS are thought to play roles in mRNA stability.

Kozak, M. (1987). An analysis of 5 -noncoding sequences from 699 vertebrate messenger RNAs. Nucleic Acids Res. 15, 8125—8148. 

The X-ray structures of other aconitases have appeared in the literature. Recently, the crystal structure of human iron regulatory protein, IRPl, in its aconitase form, has been published. Iron regulatory proteins (IRPs) control the translation of proteins involved in iron uptake, storage, and utilization by binding to specific noncoding sequences of the corresponding mRNAs known... 

The FMRl gene is located near the end of the long arm of the X chromosome. The entire gene spans 38,000 base pairs, of which only abont 4000 actnally code for amino acids in FMRP. These are collected in 17 separate exons. The bnlk of the gene is composed of noncoding sequences, introns, that are edited ont in the process of... 

Rescue experiments Target noncoding sequence 3 imtranslated regions (UTRs), alternatively 5 UTRs, can be targeted by siRNA rescue can be performed by ectopically expressed genes lacking UTRs... 

The triplets of nucleotide units in DNA determine the amino acids in a protein through the intermediary mRNA. One of the DNA strands serves as a template for synthesis of mRNA, which has nucleotide triplets (codons) complementary to those of the DNA. In some bacterial and many eukaryotic genes, coding sequences are interrupted at intervals by regions of noncoding sequences (called introns). 

Many genes in eukaryotic cells, and a few in bacteria, are interrupted by noncoding sequences called introns. The coding segments separated by introns are called exons. 

Phillip Sharp and Richard Roberts independently discovered that many genes for polypeptides in eukaryotes are interrupted by noncoding sequences (nitrons). 

Duret L, Bucher P. Searching for regulatory elements in human noncoding sequences. Curr Opin Struct Biol 1997 7 399-406. 

Generally refers to a nucleotide sequence that is complementary to a sequence of messenger RNA, which is the product of the noncoding sequence of DNA. It also refers to the peptide products from the antisense sequence referred to as antisense peptides. Antisense peptides have been investigated for biological activity. siRNA are based on the processing of antisense RNA. See Korneev, S. and O Shea, M., Natural antisense RNAs in the nervous system, Rev. Neurosci. 16, 213-222, 2005. See also MicroRNA, siRNA, Antisense Peptides, Aptamers. 

In contrast to the genes of prokaryotes, for which the coding sequences are continuous, those of eukaryotes are present in blocks (exons) separated by intervening noncoding sequences (introns). Gilbert (1978) who introduced these terms, suggested that exon/intron structure could provide a mechanism for increasing the rate of evolution. It was pointed out that if, for example, exons corresponded to units of protein function, recombination within introns could reassort protein functions to... 

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