A number of amino acids (Asp, Glu, Asn, Gln, Arg and His) have weak electronic transitions at around 210 nm. Usually, these cannot be observed in proteins because

they are masked by the more intense peptide bond absorption.

TLS Online TPP Program

#Id: 6772

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 6773

#Unit 3. Fundamental Processes

The cap binding CBP20/80 complex appears to directly bind to the mRNA export machinery (the TREX complex)

TLS Online TPP Program

#Id: 6774

#Unit 3. Fundamental Processes

(NXF1), (NXT1), SR proteins, RNA helicases, REF (RNA export factor), PABPN1 are important proteins required for mRNA transport.

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#Id: 6775

#Unit 3. Fundamental Processes

mRNP export from the nucleus into the cytoplasm is controlled by the phosphorylation and dephosphorylation of mRNP adapter proteins, REF, the NXF1/NXT1 mRNP exporter to mRNPs. 

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#Id: 6776

#Unit 3. Fundamental Processes

SR Proteins, in its phosphorylated form, the SR protein initially binds to nascent pre-mRNA. When 3′ cleavage and polyadenylation are completed, the adapter protein is dephosphorylated by a specific nuclear protein phosphatase that is essential for mRNP export. Only the dephosphorylated adapter protein can bind the mRNP exporter, thereby coupling mRNP export to correct polyadenylation.

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#Id: 6777

#Unit 3. Fundamental Processes

Mutation of either the 5′ or the 3′ invariant splice-site bases at the ends of the intron resulted in pre-mRNAs that were bound by snRNPs to form spliceosomes; however, RNA splicing was blocked, and the pre-mRNA was retained in the nucleus. 

In contrast, mutation of both the 5′ and 3′ splice sites in the same pre-mRNA resulted in export of the unspliced pre-mRNA, although less efficiently than for the spliced mRNA, probably because of the absence of an exon-junction complex. When both splice sites were mutated, the pre-mRNAs were not efficiently bound by snRNPs, and consequently, their

export was not blocked.