GCN5-dependent acetylation of HIV-1 integrase enhances viral integration.
BACKGROUND
An essential event during the replication cycle of HIV-1 is the integration of the reverse transcribed viral DNA into the host cellular genome. Our former report revealed that HIV-1 integrase (IN), the enzyme that catalyzes the integration reaction, is positively regulated by acetylation mediated by the histone acetyltransferase (HAT) p300.


RESULTS
In this study we demonstrate that another cellular HAT, GCN5, acetylates IN leading to enhanced 3'-end processing and strand transfer activities. GCN5 participates in the integration step of HIV-1 replication cycle as demonstrated by the reduced infectivity, due to inefficient provirus formation, in GCN5 knockdown cells. Within the C-terminal domain of IN, four lysines (K258, K264, K266, and K273) are targeted by GCN5 acetylation, three of which (K264, K266, and K273) are also modified by p300. Replication analysis of HIV-1 clones carrying substitutions at the IN lysines acetylated by both GCN5 and p300, or exclusively by GCN5, demonstrated that these residues are required for efficient viral integration. In addition, a comparative analysis of the replication efficiencies of the IN triple- and quadruple-mutant viruses revealed that even though the lysines targeted by both GCN5 and p300 are required for efficient virus integration, the residue exclusively modified by GCN5 (K258) does not affect this process.


CONCLUSIONS
The results presented here further demonstrate the relevance of IN post-translational modification by acetylation, which results from the catalytic activities of multiple HATs during the viral replication cycle. Finally, this study contributes to clarifying the recent debate raised on the role of IN acetylated lysines during HIV-1 infection.
Molecular Biology Laboratory, Scuola Normale Superiore, Piazza dei Cavalieri 7, 56100 Pisa, Italy. m.terreni@sns.it
Mariaelena
M
Terreni
Paola
P
Valentini
Vania
V
Liverani
Maria Ines
MI
Gutierrez
Cristina
C
Di Primio
Armida
A
Di Fenza
Valentina
V
Tozzini
Awatef
A
Allouch
Alberto
A
Albanese
Mauro
M
Giacca
Anna
A
Cereseto
D000107:Acetylation; D019943:Amino Acid Substitution; D002460:Cell Line; D055785:Gene Knockdown Techniques; D019427:HIV Integrase / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000472:pathogenicity*; D054884:Host-Pathogen Interactions; D006801:Humans; D008239:Lysine / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D016662:Virus Integration; D050880:p300-CBP Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000099224:p300-CBP-Associated Factor
D019427:HIV Integrase; D008239:Lysine; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C514801:p31 integrase protein, Human immunodeficiency virus 1