C replicative cycle

Question 1

1. Attachment

Answer 1

recpetor binding pocket of HA1 binds to N-acetyl neuraminic acid (NANA) aka sialic acid. it is terminal sugar of many glycoproteins the binding of HA to NANA has low affinity, binding of multiple HA to multiple NANA has high avidity

Question 2

1. diff serotypes of influenza have diff

Answer 2

aa residues lining the receptor binding pocket. these recognize diff linkages of NANA. for eg human influenza virus the NANA is linked to galactose by an alpha (2,6). avian influenza virus the NANA is linked by alpha (2.3)

Question 3

as well as affecting host range, diff affect tissuetropism

Answer 3

avian strains replicate in the intestines of the bird. human strains replicated in the respiratory tract only

Question 4

2. entry and uncoating

Answer 4

virus is taken up by endocytosis. endosome has prton pumps. decrease in pH in endosome causes HA2 to form a long extended alpha heliz w.the fusion peptide at the end. fusion peptides insert into endosomal membrane. HA1 pushed to sides

Question 5

2. entry and uncoating

Answer 5

HA2 separate bringing the endosomal membrane toward the viral envelope. the membrane fushes

Question 6

2. entry and uncoating

Answer 6

as pH of endosome decreases M2 ion channel is activated. protins now enter into envelope. decrease in pH causes a conformation change in M1, the genome segments released into cytoplasm

Question 7

3. role of the cells nucleus

Answer 7

most RNA viruses are replicated in cytoplasm. influenza unusual b/c rna synthesis occurs in nucleus

Question 8

3. fn of nucleocapsid proteins

Answer 8

have a sequence called nuclear localization signal, normal host cell signal used to transport proteins like DNA and RNA pol into nucleus

Question 9

3. what are genome segments coated with

Answer 9

nucleocapsid proteins

Question 10

3. how does influenza virus exploit nuclear localization signal

Answer 10

gets 8 nucleocapsid and attach P complexes into the nucleus

Question 11

4. mRNA synthesis

Answer 11

in the nucleus the mRNA is synthesized early in the infection

Question 12

4. what is the P complexes composed of

Answer 12

3 subunits. PB1 is a cap dependent RDRP. PB2 is an endonuclease. PA is a cap independent RDRP

Question 13

4. mRNA synthesis uses

Answer 13

PB1 and PB2 only

Question 14

4. PB1 requires a

Answer 14

primer

Question 15

4. fn od PB2

Answer 15

cuts of the cap and 10 nucleotide from host mRNA. called cap stealing. means host mRNA won’t be translated

Question 16

4. mRNA synthesis

Answer 16

PB1 uses the primer to synthesize +ive strand mRNA. when gets to u7 region is stutters, producing poly-a-tail. last 20 nucleotide are missing so new +ive strand cannot be used as RI

Question 17

5. protein synthesis

Answer 17

mRNA transported into cytoplasm where it translated. P complex, NP, and M1 proteins are transported into the nucleus. HA, NA and M2 are synthesized on the RER and then inserted into the cell’s membrane

Question 18

6. genome synthesis

Answer 18

as the [] of NP increases in the nucleus the P complex changes fn. PA is used instead of PB1 and PB2. PA does not need a primer it produces full length +ive strand RNA that does not have a cap or poly-a-tail

Question 19

6. how is -ive strand genome segments synthesized

Answer 19

+ive strand RI can be used by PA to synthesize -ive strand genome segments

Question 20

6. fn of NP

Answer 20

new segments are coated with NP. NP forms a helical capsid. segments are associated w/the newly synthesized P complexes and M1

Question 21

7. Assembly/exit

Answer 21

the M1, P complex and NP leave the nucleus. M1 interacts w/inner domain of HA and Na that are already inserted in the PM. each segment has a specific packaging sequence which ensures that one copy of each segment is packaged

Question 22

7. how does influenza virus exit

Answer 22

by budding

Question 23

8. maturation

Answer 23

both HA and NA are glycosylated. terminal sugar is NANA/sialic acid. if released like this visions would stick together and to cell they were exiting form. NA cleaves NANA allowing it to be transmitted to another person/cell