A late protein is a

viral protein A viral protein is both a component and a product of a virus. Viral proteins are grouped according to their functions, and groups of viral proteins include structural proteins, nonstructural proteins, regulatory proteins, and accessory proteins. Vi ...

that is formed after replication of the virus. One example is VP4 from simian virus 40 (SV40).

In Human papillomaviruses

Human papillomavirus Human papillomavirus infection (HPV infection) is caused by a DNA virus from the ''Papillomaviridae'' family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and res ...

(HPV), two late proteins are involved in

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may ...

formation: a major (L1) and a minor (L2) protein, in the approximate proportion 95:5%. L1 forms a

pentameric A pentamer is an entity composed of five sub-units. In chemistry, it applies to molecules made of five monomers. In biochemistry, it applies to macromolecules, in particular to pentameric proteins, made of five proteic sub-units. In microbiolo ...

assembly unit of the viral shell in a manner that closely resembles VP1 from

polyomavirus ''Polyomaviridae'' is a family of viruses whose natural hosts are primarily mammals and birds. As of 2020, there are six recognized genera and 117 species, five of which are unassigned to a genus. 14 species are known to infect humans, while othe ...

es. Intermolecular disulphide bonding holds the L1

capsid proteins A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may ...

together. L1 capsid proteins can bind via its nuclear localisation signal (NLS) to

karyopherin Karyopherins are proteins involved in transporting molecules between the cytoplasm and the nucleus of a eukaryotic cell. The inside of the nucleus is called the karyoplasm (or nucleoplasm). Generally, karyopherin-mediated transport occurs through ...

s Kapbeta(2) and Kapbeta(3) and inhibit the Kapbeta(2) and Kapbeta(3) nuclear import pathways during the productive phase of the

viral life cycle Viruses are only able to Replicate (biology), replicate themselves by commandeering the reproductive apparatus of cells and making them reproduce the virus's genetic structure and virion, particles instead. How viruses do this depends mainly on t ...

. Surface loops on L1

pentamer A pentamer is an entity composed of five sub-units. In chemistry, it applies to molecules made of five monomers. In biochemistry, it applies to macromolecules, in particular to pentameric proteins, made of five proteic sub-units. In microbiolog ...

s contain sites of

sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is calle ...

variation between HPV types. L2 minor capsid

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

enter the nucleus twice during infection: in the initial phase after

virion A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

disassembly, and in the productive phase when it assembles into replicated virions along with L1 major capsid proteins. L2 proteins contain two nuclear localisation signals (NLSs), one at the

N-terminal The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...

(nNLS) and the other at the

C-terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...

(cNLS). L2 uses its NLSs to

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...

with a network of

s in order to enter the nucleus via several import pathways. L2 from HPV types 11 and 16 was shown to

with karyopherins Kapbeta(2) and Kapbeta(3). L2 capsid proteins can also interact with viral dsDNA, facilitating its release from the

endocytic Endocytosis is a cellular process in which substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested material. E ...

compartment after viral uncoating.

References

{{InterPro content, IPR000784 Protein families Protein domains Proteins Viral protein class

In Human papillomaviruses

See also

References