Table 1 Methodology for creating the constructs used in the analysis

Clone pBS-CP/PR was obtained by using primers CP-PR-F and CP-PR-R on full-length RTBV clone pBSR63A and cloning the PCR fragment into plasmid pBlueScript KS.

Clone pBS-PR1 was obtained by digesting pBS-CP/PR with Xba I and Hind III and cloning the 0.8 kbp fragment into plasmid pKS.

Clone pBS-mPR1 was obtained by digesting pBS-mpr/RT 19 with Pst I and EcoR V and cloning the 0.7 kbp fragment into pBS-PR1 digested with Pst I and EcoR V.

Clone pBS-CP/mPR was obtained by digesting pBS-mPR1 with Pst I and EcoR V and cloning the 0.7 kbp fragment into pBS-CP/PR digested with Pst I and EcoR V.

Cloning into pTrHis.

Clone pTr-CP/PR was obtained by digesting pBS-CP/PR with BamH I and Hind III and cloning the 2.5 kbp fragment into pTrHisA digested with BamH I and Hind III.

Clone pTr-PR was obtained was obtained by using primers Ab-PR-F and Ab-PR-Ron full-length RTBV clone pBSR63A and cloning the PCR fragment into pTrHis A digested with Nco I and Hind III.

Clone pTr-mPR was obtained by using primers Ab-PR-F and Ab-PR-R on plasmid pBS-mpr/RT and cloning the PCR fragment into pTrHis A digested with Nco I and Hind III.

Cloning into pET.

Clone pET-MP was obtained by using primers Et-MP-F and Et-MP-R on full-length RTBV clone pBSR63A and cloning the PCR fragment into pET-28a digested with NdeI and BamHI.

Clone pET-MP/PR was obtained by digesting pBS-CP/PR with Sca I and Hind III and cloning the 2.3 kb fragment into pET-MP digested with Sca I and Hind III.

Clone pET-MP/mPR was obtained by digesting pBS-CP/mPR with Sac I and Hind III and cloning the 2.3 fragment into pET-MP.

Clone pET-P3 was obtained by different steps. First, Pst I digested product (2.1 kbp) from pBS-PR/RT [19] containing PR and RT was cloned at the Pst I site of pTr-CP/PR. The resulting plasmid was digested by BamH I, and the 3.9 kb fragment was clone into pTrHis A, to obtain pTr-CP-RT. The later was digested with Sca I and BamH I and the 3.8 fragment was cloned into pET-MP digested with Sca I and BamH I to obtain pET-P3.

Clone pET-mP3 was obtained using the same strategy than above, by using pBS-mpr/RT instead of pBS-PR/RT.

Lists of primers

CP-PR-F : 5'-GAAAGAGGGATCCAAAATGGCAATAGTAGAAG-3'

CP-PR-R : 5'-GTTTTTCAAAAGCTTCTTAATCTGCTGGCGTG-3'

Ab-PR-F: 5'-CATGCCATGGCACATCATCATCATCATCATCATGCAGGATGTTATGTA-3'

Ab-PR-R : 5'-TATTCCCGAAGCTTTTTATATAGTTATATAATC-3'

Et-MP-F : 5'-GTAAGTGCCCATATGAGCCTTAGACCATTTACTGG-3'

Et-MP-R : 5'-AGGGCTGTGGGATCCTCATTCAGGTCTATCACCTC-3'