High impact information on CBP2

• Folding energy provided by CBP2 drives assembly of two RNA domains that comprise the catalytic core and meditates association of an approximately 100 nt 5' domain that contains the 5' splice site [1].
• CBP2 is an RNA tertiary structure binding protein required for efficient splicing of a yeast mitochondrial group I intron [2].
• The yeast CBP2 gene product is required for the splicing of the terminal intron (bI5) of the mitochondrial cytochrome b pre-mRNA in vivo [3].
• In vitro, bI5 RNA self-splices efficiently only at high MgCl2 concentrations (50 mM); at 5 mM MgCl2, efficient splicing requires purified CBP2 protein [3].
• The amino acid sequence of the putative ORF1 product does not exhibit any homology with other known proteins, except for a small region of homology with the gene product of another nuclear yeast gene involved in mitochondrial RNA splicing, CBP2 [4].

Biological context of CBP2

• These results confirm that CBP2 codes for a protein specifically required for splicing of the cytochrome b intron and further suggest that absence of the intervening sequence does not noticeably affect the expression of respiratory function in mitochondria [5].
• This reading frame is proposed to code for the CBP2 gene product [6].
• A recombinant plasmid with the CBP2 gene has been selected from a library of wild type nuclear DNA and further subcloned by transformation of a cbp2 mutant to respiratory competency [6].
• Also the S. douglasii and S. cerevisiae CBP2 genes are completely interchangeable, even though the intron bI5 is absent from the S. douglasii mitochondrial genome [7].
• We have demonstrated that inactivation of the S. cerevisiae CBP2 gene affects the maturation of the S. douglasii LSU pre-RNA, leading to a respiratory-deficient phenotype in the hybrid strains [8].

Anatomical context of CBP2

• The CBP2 protein has been partially purified from wild-type yeast mitochondria and shown to promote splicing at physiological concentrations of Mg2+ [9].

Associations of CBP2 with chemical compounds

• Guanosine 5'-monophosphate binds (Kd approximately 0.3 mM) with the same affinity to bI5 and the bI5-protein complex, supporting independent binding of the nucleophile and CBP2 [10].
• Hydroxyl radical footprinting demonstrates that assembly with the CBP2 protein cofactor chases the RNA from the collapsed state to the native state [11].

Physical interactions of CBP2

• We propose that the CBP2 protein binds to the bI2 precursor, thereby stabilizing the catalytically active structure of the RNA [9].

Other interactions of CBP2

• Excision of bI2 in vivo, however, requires a protein encoded by the nuclear gene CBP2 [9].
• The fifth and terminal intron of yeast cytochrome b pre-mRNA (a group I intron) requires a protein encoded by the nuclear gene CBP2 for splicing [12].

Analytical, diagnostic and therapeutic context of CBP2

• In contrast, most mutations affecting the ligation of exons were suppressed in vitro by Cbp2 [13].

References