The occurrence of translation mechanism in the cytosol offers advantages to mRNA transfer over DNA-based transfection in nondividing cells. Here, we sought to optimize mRNA constructs allowing a high level of protein upon lipofection. We found that luciferase into mouse dendritic cells (JAWSII cells) was similar to 20-fold higher when the luciferase mRNA was capped with 3'-O-methyl-m7(5')GpPP(5')G (anti-reverse cap analogue; ARCA) than with m7(5')Gppp(5')G (CAP). Adding a Poly(A) tail of 100 instead of 64 adenosines in cis increased by similar to 35-fold more the protein level. Finally, ARCA-Luc-mRNA-A100 construct was 700-fold better efficient than the CAP-Luc-mRNA-A64 one. Moreover, co-transfection with free Poly(A) chains in trans enhanced by 100% the luciferase level. The efficiency of ARCA-mRNA-A100 construct was validated in immature and mature human CD34-derived dendritic cells. Such mRNA construct was also successful to obtain high level of MART-I tumor antigen. (c) 2005 Elsevier Inc. All rights reserved.