Virgin Atlantic to Virgin America

I'm looking to fly MAN/SFO via LAS but am concerned about switching between a V. Atlantic to a V. America flight and have the following questions..
1. If I book as a through ticket will I have to recheck my bags at LAS?
2. If I miss the connection at LAS who is responsible?

However you arrive into the US at your first port of call you have to clear immigration and customs, so with this itinerary you will go through immigration, pick up your bags, transfer to the VX terminal and recheck - same for any airline really although some have recheck desks conveniently outside customs.

If you book your trip on one PNR and are late into LAS, then VS/VX will take responsibility for getting you on to SFO. If you book separate tickets then it's your responsibility.

Thank you!