title: Translational fusion and redirection to thylakoid lumen as strategies to enhance accumulation of human papillomavirus E7 antigen in tobacco chloroplasts.
abstract: Human papillomavirus (HPV) is the causal agent of cervical cancer, one of the most common causes of death in women worldwide, and its E7 antigen is the major candidate for a therapeutic vaccine. The large scale production of E7 by molecular farming that would lead to the development of a safe and inexpensive vaccine is impaired by its low accumulation level in the plant cell. To enhance antigen production in the plastids, two alternative strategies were carried out: the expression of E7 as a translational fusion to β-glucuronidase enzyme and redirection of E7 into the thylakoid lumen. The use of the β-glucuronidase as a partner protein turned out to be a successful strategy, antigen expression levels were enhanced between 30 and 40 times relative to unfused E7. Moreover, best accumulation, albeit at a high metabolic cost that compromised biomass production, was obtained redirecting E7 into the thylakoid lumen by the incorporation of the N-terminal transit peptide, Str. Following this approach lumenal E7 production exceeded the stromal by two orders of magnitude. Our results highlight the relevance of exploring different strategies to improve recombinant protein stability for certain transgenes in order to exploit potential advantages of recombinant protein accumulation in chloroplasts.
authors: Instituto de Ingeniería Genética y Biología Molecular "Dr, Hector Torres" (INGEBI-CONICET), Vuelta de Obligado 2490, C.C 1428ADN, Ciudad Autónoma de Buenos Aires, Argentina.
authors: Mauro
authors: M
authors: Morgenfeld
authors: Ezequiel
authors: E
authors: Lentz
authors: María Eugenia
authors: ME
authors: Segretin
authors: E Federico
authors: EF
authors: Alfano
authors: Fernando
authors: F
authors: Bravo-Almonacid
mesh_terms: D002736:Chloroplasts / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D005966:Glucuronidase / Q000235:genetics; D050725:Papillomavirus E7 Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D030821:Plants, Genetically Modified / Q000254:growth & development; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D050725:Papillomavirus E7 Proteins; D011993:Recombinant Fusion Proteins; C059731:oncogene protein E7, Human papillomavirus type 16; D005966:Glucuronidase