Roll Call (subscription required) describes the DISCLOSE Act like so:
The bill will essentially heavily restrict the political activities of 501(c)(4) organizations, unless--as in the case of the NRA--they're able to carve out a special exemption for themselves. RedState has many more details.
The bill... comes in response to the high court’s 5-4 ruling in Citizens United v. Federal Election Commission in January that struck down many restrictions on political communications and the groups that fund them. The proposal would bulk up disclosure, political coordination and disclaimer requirements, and impose new limits on political involvement by government contractors and foreign governments.
As Erick Erickson wrote yesterday, it seems "the NRA is selling out the Constitution in the name of self preservation." In the end, it's disappointing that the NRA won't stand up for everyone's First Amendment rights as fervently as they fight for everyone's Second Amendment rights.