27 and 29 September, 2006

Chapter 11

Transposition and Site-Specific Recombination

Overview• Conservative Site-Specific Recombination (CSSR) may involve

insertion, deletion, or inversion of DNA sequences.• Site-specific recombinases have a mechanism that includes a DNA-

protein covalent intermediate.• CSSR may be regulated by the presence or absence of accessory

proteins.• Resolvases are CSSR recombinases that disentangle circular

chromosomes.• Transposons move using recombination pathways.• Transposons may be autonomous or nonautonomous.• DNA transposons and viral-like retrotransposons move via a cut/paste

mechanism.• Retrotransposon movement involves reverse transcription.• Some transposons regulate copy number or control target site selection

through the use of proteins or antisense RNA.• V(D)J recombination uses regulated, specific recombination to generate

immune diversity.

Recombination and Transposition

CSSR: Prophage Insertion

Three Classes of CSSR

Recombinase Recognition Sites

Recombinase Mechanism

Serine Recombinases

Tyrosine Recombinases

Mechanism of Cre

Recombinase

Cre-DNA Structure

Lambda integration

requires architectural

proteins.

Int and IHF stabilize bent

DNA.

Hin Inversion

Hin inversion requires Fis bound at an enhancer.

Resolvases disentangle circular DNAs after replication.

FtsK Regulation of

the Xer Resolvase

Mechanism

FtsK is present at the division closure site.

Conservative and Replicative Transposition

Transposons in Several Genomes

Types of Transposons

Cut and Paste Transposition

Three Mechanisms for Cleaving the Nontransferred Strand

Replicative Transposition

Retrotransposon Movement

Retrotransposon Movement

Retrotransposon Movement

DNA Transposases and retroviral integrases are members of the same protein superfamily.

LINE poly-A Retrotransposon

Movement

Tn10 achieves antisense copy control by overlapping promoters.

Antisense Copy

Control

Tn10 transposase promoter is active only

when hemimethylated.

MuA and MuB participate in selecting Mu transposition

target sequences.

MuA disrupts MuB assembly,

conferring transposition

target immunity.

Clustered Integration of Yeast Ty Elements

Antibody

V(D)J Recombination

Recombination Signal Sequences

V(D)J Recombination

Mechanism

Title

LINES and SINES Again?