Lecture 4: Mobile Introns and Inteins

BIOC 4403

mobile genetic elements

types of DNA that can move around in the genome; common examples include transposons ("jumping genes") and plasmids

Group 1 introns

\-Found in rRNA

\-Self splicing

\-Ribozymes

\-diverse but not common

Homing

lateral or horizontal transfer of an intervening sequence to an intron lacking version of the gene

homing endonuclease

Recognize and cleave 12-40bp DNA sequence motifs

Recognize genes lacking intron

Group 1 intron intermediate

LINEAR

Inteins

Protein segments that are removed from the final protein

Exteins

The protein segments that are kept and spliced together

Ectopic transposition

Movement of intron to a new genomic site

How can ectopic transposition occur?

Reverse splicing into another RNA

Reverse Tc

Recombination of cDNA into genome by recombination / repair enzymes

Group 2 introns

protein-encoding genes in mitochondria and chloroplasts, self-splicing

Similar to spliceosomal

Group 2 introns intermediate

LARIAT

Intron encoded protein

Functions as RNP complex bound to intrinsic RNA that encoded it

Mediates homing to intron-minus location

protein splicing

removal of part of polypeptide before folding