The invention relates to compositions comprising mixtures of polypeptides having reverse transcriptase (RT) activity and to methods of producing, amplifying or sequencing nucleic acid molecules using these compositions or polypeptides, particularly at temperatures above about 55 C. The invention also relates to nucleic acid molecules produced by these methods, to vectors and host cells comprising these nucleic acid molecules, and use of such nucleic acid molecules to produce desired polypeptide. The invention also relates to methods for producing Avian Sarcoma-Leukosis Virus (ASLV) RT subunits, in particular, Avian Myeloblastosis Virus (AMV) RTs, to isolated nucleic acid molecules encoding ASLV RT subunits, and to ASLV RT subunits produced by these methods. The invention further relates to nucleic acid molecules encoding recombinant RT holoenzymes, particularly ASLV RTs, methods for producing these RTs and to RTs produced by these methods. The invention also relates to kits comprising the compositions, polypeptides, and ASLV RTs of the invention.