I am in San Francisco and I have a commercial lease ending 31 May 2012.
I pay the lease monthly.
In past years I would get a 30-60day notice to renew for the year and usually the rent would decrease by a little.
This year I received a 3 day notice and the rent was increased by 25%.
Is my leasing company required to give me at least 30days notice before increasing rent?

There are no laws for commercial leases like there are for residential leases. Your tenancy is governed by the terms of the lease itself as well as past dealings with the landlord.

What does your lease say about the end of the term? Does it require that the parties give each other a specific amount of notice if they do not choose to renew the lease? If the lease requires a 30 or 60 day notice if one of the parties does not intend to renew then that is the same time that the landlord must give you for notice of a rent increase.

If the lease does not require a time for notice of non-renewal then a judge would probably find that you are entitled to 30 or 60 days notice since that is how the landlord has operated in the past. But this is not a definite thing and you are taking a chance if you rely on that.

Have you spoken with the landlord and tried to negotiate a new rent amount? Your first step should be carefully reading every word of the lease and your second step should be to try and work out an agreement with the landlord.