I am looking for an explanation of why do we use house keeping genes (e.g: B-actin) as loading control. I read that it has a long half life that exceeds most proteins, but Still I found papers doing the assay for time points exceeding b-actin half life and although they show a gradual decrease in protein of interest with equal bands of b-actin. I think normalizing the sample load to b-actin would not reflect the true amount of protein of interest solely due to it eventually responding to the treatment and in return decreasing over the course of time.

What about a protein that has a half-life close to the b-actins'? wouldn't they show equal bands over the course of time.

What do you think?