I would guess that any cell transfected with the right components (envelope,...) should be able to produce a virus -as far as I remember 293 cell were particularly suitable, as they already contain some viral proteins - here an excerpt from Wikipedia (still think it's a good resource for stuff like that):

"A more specific use of HEK 293 cells is in the propagation of adenoviral vectors. Viruses offer an extremely efficient means of delivering genes into cells, since this is what they have evolved to do, and are thus of great use as experimental tools. However, as pathogens, they also present a degree of danger to the experimenter. This danger can be avoided by the use of viruses which lack key genes, and which are thus unable to replicate after entering a cell. In order to propagate such viral vectors, a cell line that expresses the missing genes is required. Since HEK 293 cells express a number of adenoviral genes, they can be used to propagate adenoviral vectors in which these genes (typically, E1 and E3) are deleted, such as AdEasy.[12]

An important variant of this cell line is the 293T cell line that contains the SV40 Large T-antigen, that allows for episomal replication of transfected plasmids containing the SV40 origin of replication. This allows for amplification of transfected plasmids and extended temporal expression of the desired gene products. Note that any similarly modified cell line can be used for this sort of work; HeLa, COS and Chinese Hamster Ovary cell are common alternatives.[citation needed] HEK 293, and especially HEK 293T, cells are commonly used for the production of various retroviral vectors. Various retroviral packaging cell lines are also based on these cells."

of course the fact that 293 cells can be transfected much more easily and cost effect than many other cells also helps

in general, I always think it's great to ask questions like that and believe that thinking about this stuff rather than simply following established protocols is indicative of the scientific curiosity a scientist should have - maybe not so much wanted in a tech however - anyways, one always has to be a balance between trying new things and optimizing protocols and simply doing it the way it has always been done because it works well enough

Whoa!! That was a bit rude.. I am not sure why you were offended by it so much.. That was a question!!! If you can't answer it then I would advice not to rather than replying something like this.. Don't tell me you always follow the book and never take any shortcuts!!! I am just openly saying it whereas you are not..!! Anyways thanks for your advice.. And just to let you know, I am very much hopeful for my future in science unlike yours although you seem to be a "Post Doc" and I seriously don't know how!!!

I would guess that any cell transfected with the right components (envelope,...) should be able to produce a virus -as far as I remember 293 cell were particularly suitable, as they already contain some viral proteins - here an excerpt from Wikipedia (still think it's a good resource for stuff like that):

"A more specific use of HEK 293 cells is in the propagation of adenoviral vectors. Viruses offer an extremely efficient means of delivering genes into cells, since this is what they have evolved to do, and are thus of great use as experimental tools. However, as pathogens, they also present a degree of danger to the experimenter. This danger can be avoided by the use of viruses which lack key genes, and which are thus unable to replicate after entering a cell. In order to propagate such viral vectors, a cell line that expresses the missing genes is required. Since HEK 293 cells express a number of adenoviral genes, they can be used to propagate adenoviral vectors in which these genes (typically, E1 and E3) are deleted, such as AdEasy.[12]

An important variant of this cell line is the 293T cell line that contains the SV40 Large T-antigen, that allows for episomal replication of transfected plasmids containing the SV40 origin of replication. This allows for amplification of transfected plasmids and extended temporal expression of the desired gene products. Note that any similarly modified cell line can be used for this sort of work; HeLa, COS and Chinese Hamster Ovary cell are common alternatives.[citation needed] HEK 293, and especially HEK 293T, cells are commonly used for the production of various retroviral vectors. Various retroviral packaging cell lines are also based on these cells."

of course the fact that 293 cells can be transfected much more easily and cost effect than many other cells also helps

in general, I always think it's great to ask questions like that and believe that thinking about this stuff rather than simply following established protocols is indicative of the scientific curiosity a scientist should have - maybe not so much wanted in a tech however - anyways, one always has to be a balance between trying new things and optimizing protocols and simply doing it the way it has always been done because it works well enough

Hi Emanuel.. Thank you so much for such a detailed explanation.. Yeah I was thinking of a reason why it doesn't work properly in other cell lines.. and as you mentioned, it might be because they can express adenoviral genes.. But yeah I will have to think of some solution as I have to package a approx. 120 shRNAs.. I can't be doing it at one go as far as I understood the concept.. Anyways, that was a useful bit of information.. Thank you..

Excuse me Matthew but I am not having just one shRNA to package.. Probably you are so good at these that you can do everything in just a single day.. Unfortunately I am a Masters student and I have just 6 months to complete my thesis and I can't be packaging the particles when my work is to do screening with shRNAs.. It would be nice if you could avoid replying to this message or this thread.. Thank you..

Hey Matthew.. Let me be clear.. My HeLa cells have a silenced GFP attached to CMV promoter.. So the viral particles get packaged in HeLa cells, I can directly view them under microscope or FACS them to check for GFP expression from which I can identify the potential hits directly. If I use HEKs, I need to infect them first, take the particles from supernatant and then infect HeLa with those particles. Since my HEK cells don't have a silenced GFP it is difficult for me to screen them.

Sorry to have addressed you again but I can't stop laughing thinking how dumb you are.. Just bcos everyone says it works please don't follow blindly.. Ask questions coz that's what people in our field do.. Guess you don't know that.. Probably thats how you got your PhD.. Anyways hope you understood why I said "too much work"

I didn't think I would have to say this in this forum but: stop it, guys - and I don't care who started it!