53. NF-kB is a transcription factor that plays a pivotal role inimmune response and inflammatory response. In itsresting state, NF-kB is rendered inactive in the cytosolby bound with lKB. When cell is treated with TNF-a, lkBgets phosphorylated by 1K and subsequently degradedby proteasome. NF-KB thus becomes free and translocates to the nucleus and gets activated. In anexperiment, a cell is subjected to the followingtreatment:
A. TNF-α
B. TNF-α+ proteasome inhibitor
C siRNA for lkb + TNF- α
D. siRNA for lKK+TNF- α
What will be the best-fit graph for NF-kB activity if it is measured by NF-kB luciferase assay?

Introduction

NF-κB is a critical transcription factor involved in immune and inflammatory responses. Under resting conditions, NF-κB is sequestered in the cytosol by its inhibitor IκB. Upon TNF-α stimulation, IκB kinase (IKK) phosphorylates IκB, leading to its ubiquitination and degradation by the proteasome. Freed NF-κB translocates to the nucleus and activates gene transcription.

Treatment Conditions and Expected NF-κB Activity

• A. TNF-α: Normal pathway activation — IKK phosphorylates IκB, causing its degradation, thus allowing NF-κB to translocate into the nucleus, resulting in high NF-κB activity.

• B. TNF-α + Proteasome Inhibitor: IκB is phosphorylated but not degraded due to proteasome inhibition, so NF-κB remains bound and inactive in the cytosol. Expect low NF-κB activity despite TNF-α stimulation.

• C. siRNA for IκB + TNF-α: Knockdown of IκB means less inhibitor is present; even without TNF-α, NF-κB can translocate. Upon TNF-α treatment, expect high or enhanced NF-κB activity compared to (A).

• D. siRNA for IKK + TNF-α: IKK knockdown prevents phosphorylation of IκB, thus IκB is not degraded and NF-κB remains inactive. Expect low NF-κB activity similar to (B).

Summary of Expected NF-κB Luciferase Activity Levels

• (A) High

• (B) Low

• (C) High or higher than (A)

• (D) Low

Visualization of Results

A graph of NF-κB luciferase activity (y-axis) vs treatment groups (x-axis) will show:

• High bars for groups (A) and (C),

• Low bars for groups (B) and (D).