Q5 DNA polymerase is appropriate for upto 20 kb DNA amplicons.

https://www.google.co.in/url?sa=t&source=web&rct=j&url=https://www.neb.com/brochures/pcr-brochure&ved=0ahUKEwjgsvWHipXVAhXDj5QKHSpgBVgQFgg6MAQ&usg=AFQjCNGOYpfax68lBzE6r8VaF2lmkZyNqw

Though, I have never worked with Yeast two hybrid systems.

Hi!

l would recommend you Taq Polim High fidelity system, wich is one of the most used in Dna sequencing.

Salam. I have previously amplified 7.3Kb using NeoTaq Polymerase (Takara). Just last week, I have amplified ~4kb using a Hi-Fi(Hi-Fidelity) Taq DNA Polymerase (ThermoFisher). Best wishes.

Hi. In the following paper from 1997 they use 2000 amino acids (or 6 KB DNA) of Gcn1 in a 2-hybrid construct

mcb.asm.org/content/17/8/4474.full.pdf

see Figure 8

Thanks everyone for your information.

Oyalikum assalam, Sharmin. Did you amplify from cDNA. If so, then could you please let me know whether you used cDNA synthesis kit that generates long cDNAs as many of the cDNA systhesis kit like tetro reverse transcriptase generate cDNAs where there would be less representation of the 5' end of the long cDNAs if oligo DTs are used for RT reaction.

Thanks in advance for any comments and suggestion on this.

Yes brother. I have used cDNA dilution of 5X and 10X. I have used Superscipt III cDNA synthesis kit from Invitrogen. Rather than using random hexamers, I have used Oligo-dT without any glitch. The kit contained both random hexamers/Oligo-dT, so you can try both if you have any doubt. Best wishes for your outcome.