The HA-tag is a protein tag derived from the human influenza hemagglutinin (HA) protein, which allows the virus to target and enter host cells. An HA-tag is composed of a peptide derived from the HA-molecule corresponding to amino acids 98-106, which can be recognized and selectively bound by commercially available antibodies. This makes HA a powerful tool in molecular biology, commonly included in expression vectors and in the production of recombinant proteins. [1] Like other epitope tags, HA-tag is small and generally does not alter the traits of proteins it is attached to. [2] As a result HA-tags are often used to identify protein-protein interactions or to detect protein expression, using Co-Immunoprecipitation or Western blot respectively. [3] [4]
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The HA-tag is not suitable for detection or purification of proteins from apoptotic cells since it is cleaved by Caspase-3 and / or Caspase-7 after its sequence DVPD, causing it to lose its immunoreactivity. [5] Labeling of endogenous proteins with HA-tag using CRISPR was recently accomplished in-vivo in differentiated neurons. [6]
