Help regarding cell line - (Sep/15/2010 )

Why do we 1st make pseudovirus i.e vector in 293T cells and then harvest it and then infect the HeLa cells for creating stable cell line.Why can't we directly infect HeLa cells with the plasmid of our interest?

You first transfect the vector into the 293T cells to make the adenovirus. This cell line contains the E1A and E1B genes necessary for the virus to propagate. You really should google "293 adenovirus" and learn more about this if you are going to be working with virus. You then harvest the adenovirus from the 293 cells and use this to infect the HeLa cells. Since the HeLa cells are lacking the essential E1A and E2B genes, the virus will simply infect the cells but not replicate. Transfecting the vector into HeLa cells will not create virus or produce your desired protein.