Part:BBa_K4235001

Polyhedrin Promoter

Usage and Biology

Normally, the polyhedrin promoter drives the expression of the polyhedrin protein in baculoviruses, which is critical to maintain the pathogenicity and protect the virions from harsh environments. The polyhedrin protein matrix breaks down in alkaline conditions, disrupting the crystal-like viral capsule and releasing viral particles in the environment.

Given the importance of the polyhedrin promoter, it is no surprise that its expression is driven by one of the most powerful promoters found in baculoviruses. This makes the polyhedrin promoter highly desirable for expression of heterologous genes. The Baculovirus expression systems frequently exploit the polyhedrin promoter for large scale production of recombinant proteins. While many details of the exact mechanism of this promoter are unknown, below are some of the functionally relevant parts of the promoter: A TAAG sequence is found in the polyhedrin promoter, which is essential for its identification by the baculovirus RNA polymerase. Mutations in the TAAG motif are known to abolish expression in reporter genes. CAGT sequence is conserved in nearly all baculovirus promoters and functions as a transcription initiation site. A CAGT sequence is present downstream of the transcriptional start site of the polyhedrin promoter. Burst sequence: An AT rich sequence present between the TAAG transcription start site and the ATG translation initiation site of the p10 and polyhedrin promoters. Assists in the burst transcription of viral genes in the very late phase of infection. PPBP (polyhedrin promoter binding protein): PPBP is a transcription factor which binds to the AATAAATAAGTATT sequence which contains the transcription initiation site (TAAG) in p10 and polyhedrin promoters. VLF-1: This transcription factor plays a regulatory role in very late phase gene expression by binding to the burst sequence found in the p10 and the polyhedrin promoters. Overexpressing VLF-1 and increasing the number of burst sequences results in an enhanced expression of the downstream gene.

References:

Putman, Z. (2020, November 15). Evaluating modified polyhedrin promoters for improved co-expression of KRAS4b. Maryland Shared Open Access Repository Home. Retrieved August 2, 2022, from https://mdsoar.org/handle/11603/20062

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]