Question 1

Which of the following is thought to be the reservoir for human papilomaviruses?

Accepted Answer

Human papillomaviruses (HPVs) are primarily associated with the human genital tract, affecting both males and females. They are known to infect the skin and mucous membranes of the genitals, making both male and female genital tracts reservoirs for these viruses.

Question 2

Which of the following describes the mechanism used by the E6 protein of papillomaviruses to remove the p53 protein.

Accepted Answer

The E6 protein of papillomaviruses promotes the ubiquitination of the p53 protein, leading to its degradation by the proteasome.

Question 3

The E2 protein from papillomaviruses can bind to the viral DNA and to mitotic chromosomes.What purpose might this serve for the virus?

Accepted Answer

The ability of the E2 protein to bind to mitotic chromosomes allows the viral DNA to segregate to each daughter cell during cell division, ensuring that the virus can replicate and spread.

Question 4

When the late promoter of papillomaviruses is activated,it increases production of the E1 and E2 proteins.Which of the following explains why an increase in these two proteins would contribute to vegetative replication of the virus?

Accepted Answer

The E1 and E2 proteins are involved in initiating DNA replication of the viral genome. Therefore, an increase in these proteins would contribute to vegetative replication of the virus.

Question 5

The E7 protein from papillomavirus stabilizes the cellular p53 protein,which leads to cell cycle arrest.Which of the following explains the mechanism by which p53 causes cell cycle arrest?

Accepted Answer

p53 activates transcription of the p21 gene, which encodes for the p21 protein. The p21 protein inhibits cyclin-dependent kinases (CDKs), which are required for progression through the cell cycle. Specifically, p21 prevents the phosphorylation of the retinoblastoma protein (pRb), which is needed for the release of transcription factor E2F, thus inhibiting cell cycle progression.

Question 6

Papillomaviruses replicate in differentiated keratinocytes,which are not actively dividing.How does the virus handle this situation?

Accepted Answer

The viral E7 protein binds to the pRb protein, which normally suppresses cell cycle progression. By binding to pRb, E7 inactivates its ability to prevent entry into S phase, thus promoting cell cycle progression and allowing the virus to replicate its genome. This occurs in differentiated keratinocytes, which are normally post-mitotic and not actively dividing.

Question 7

The E6 proteins from highly oncogenic papillomaviruses have been shown to interact with cellular proteins,which control cell polarity and proliferation,that contain which of the following protein domains?

Accepted Answer

The E6 proteins from highly oncogenic papillomaviruses have been shown to interact with cellular proteins that contain PDZ domains. PDZ domains are protein interaction motifs that are capable of recognizing short linear motifs in proteins and regulating intracellular signaling pathways. Therefore, the best choice in this scenario is E.

Question 8

Which of the following proteins from papillomavirus can bind to the viral origin of DNA replication and unwind the DNA strands?

Accepted Answer

E1 is a helicase protein that can bind to the viral origin of DNA replication and unwind the DNA strands. E2 protein binds to the origin and helps in the recruitment of other factors necessary for DNA replication. E6 and E7 proteins are involved in the regulation of cell growth and proliferation, while L1 protein forms the capsid of the virus.

Question 9

In papillomaviruses,plasmid replication produces a large number of viral genomes which will be packaged into new virions.

Accepted Answer

Papillomaviruses do not replicate using plasmids. They have a double-stranded DNA genome that replicates using host cellular machinery. The new viral genomes produced during replication are encapsidated into new virions.

Question 10

The human papillomavirus can produce condylomas.What is the more common term to describe this type of skin lesion?

Accepted Answer

Genital warts are the more common term used to describe this type of skin lesion caused by the human papillomavirus.

Question 11

The papillomaviruses used to be classified in the same family as the polyomaviruses.Which of the following is a feature that distinguishes them from polyomaviruses?

Accepted Answer

The answer of The papillomaviruses used to be classified in...

Question 12

The E7 proteins from the oncogenic strains of papillomaviruses bind to pRb more tightly than the E7 proteins from nononcogenic strains of the virus.

Accepted Answer

This is true, as the high-risk or oncogenic strains of papillomaviruses have E7 proteins with a higher affinity for pRb, leading to the disruption of the pRb-E2F complex and subsequent cell cycle progression, ultimately resulting in cellular transformation and cancer.

Question 13

Mutations in the p53 gene are seen in over 50% of human tumors.

Accepted Answer

Mutations in the p53 gene are a common genetic change seen in many types of human tumors, occurring in over 50% of cases. This gene normally plays a critical role in regulating cell growth and preventing the development of cancer, but when mutations occur, it can lead to uncontrolled cell proliferation and eventually tumor formation.

Question 14

The currently available HPV vaccines contain virus-like particles composed of which of the following?

Accepted Answer

The currently available HPV vaccines contain virus-like particles composed of the L1 protein alone. These virus-like particles are non-infectious because they lack the viral DNA, but they can still stimulate the immune system to produce antibodies against HPV.

Question 15

Which of the following cellular events causes the papillomavirus to enter "vegetative replication"?

Accepted Answer

Papillomavirus enters vegetative replication when the infected keratinocytes undergo terminal differentiation. This process allows the virus to replicate its DNA and produce viral proteins necessary for assembling new virus particles in the upper layers of the epithelium.

Question 16

Which of the following describes the form that the papillomavirus genome is found in most cervical cancer cells?

Accepted Answer

The answer of Which of the following describes the form...

Question 17

Productive infections with human papillomaviruses have been difficult to study in cultured cells.Which of the following explains why?

Accepted Answer

Productive infections with human papillomaviruses only occur in differentiated keratinocytes, which are difficult to maintain in cell culture.

Question 18

Which of the following describes the best treatment for papillomavirus induced cervical lesions?

Accepted Answer

Treatment of papillomavirus induced cervical lesions typically involves removal of the lesion using a laser, known as a loop electrosurgical excision procedure (LEEP), or a cold knife conization. Vaccination with the vaccine against HPV is important for prevention, but is not a treatment for existing lesions. Radical surgery (hysterectomy) is only required for severe cases or if there is evidence of cancer. Injection of antibodies against HPV into the lesion and systemic anticancer drugs are not effective treatments for cervical lesions caused by HPV.

Question 19

The cultured human cell line HeLa expresses the E6 and E7 proteins of human papillomavirus.What would happen to these cells if the expression of these proteins was shut off?

Accepted Answer

The E6 and E7 proteins of human papillomavirus are known to inactivate tumor suppressor proteins like p53 and Rb, allowing the cells to bypass normal cell cycle checkpoints and avoid apoptosis. If the expression of these proteins is shut off, the cells would likely undergo apoptosis due to the reactivation of these tumor suppressor pathways.

Question 20

Cervical tumors caused by human papillomavirus do not show the typical mutations in the p53 gene that most cancer cells have.Which of the following explains why?

Accepted Answer

The E6 protein encoded by human papillomavirus causes the degradation of the p53 protein, preventing its typical tumor suppressor function.

Quiz 22: Papillomaviruses